One of the memos is from 2002, the other three are from 2005.

According to the AP:

One memo specifically authorized a method for combining multiple techniques, a practice human rights advocates argue is particularly harmful and crosses the line into torture even if any of the individual methods do not.

...

The methods include keeping detainees naked for long periods, keeping them in a painful standing position for long periods, and depriving them of solid food. Other tactics included using a plastic neck collar to slam detainees into walls, keeping the detainee's cell cold for long periods, and beating and kicking the detainee. Sleep-deprivation, prolonged shackling, and threats to a detainee's family were also used.

Among the things not allowed in the memo were allowing a prisoner's body temperature or caloric intake to fall below a certain level, because either could cause permanent damage, the officials said.

The techniques were applied to 14 suspects considered very senior terrorists.

In addition, the Justice Department announced in a statement that CIA employees won't be tried for waterboarding.

Here's the full statement from the White House. The statement from DOJ follows it.

Statement of President Barack Obama on Release of OLC Memos

The Department of Justice will today release certain memos issued by the Office of Legal Counsel between 2002 and 2005 as part of an ongoing court case. These memos speak to techniques that were used in the interrogation of terrorism suspects during that period, and their release is required by the rule of law.

My judgment on the content of these memos is a matter of record. In one of my very first acts as President, I prohibited the use of these interrogation techniques by the United States because they undermine our moral authority and do not make us safer. Enlisting our values in the protection of our people makes us stronger and more secure. A democracy as resilient as ours must reject the false choice between our security and our ideals, and that is why these methods of interrogation are already a thing of the past.

But that is not what compelled the release of these legal documents today. While I believe strongly in transparency and accountability, I also believe that in a dangerous world, the United States must sometimes carry out intelligence operations and protect information that is classified for purposes of national security. I have already fought for that principle in court and will do so again in the future. However, after consulting with the Attorney General, the Director of National Intelligence, and others, I believe that exceptional circumstances surround these memos and require their release.

First, the interrogation techniques described in these memos have already been widely reported. Second, the previous Administration publicly acknowledged portions of the program - and some of the practices - associated with these memos. Third, I have already ended the techniques described in the memos through an Executive Order. Therefore, withholding these memos would only serve to deny facts that have been in the public domain for some time. This could contribute to an inaccurate accounting of the past, and fuel erroneous and inflammatory assumptions about actions taken by the United States.

In releasing these memos, it is our intention to assure those who carried out their duties relying in good faith upon legal advice from the Department of Justice that they will not be subject to prosecution. The men and women of our intelligence community serve courageously on the front lines of a dangerous world. Their accomplishments are unsung and their names unknown, but because of their sacrifices, every single American is safer. We must protect their identities as vigilantly as they protect our security, and we must provide them with the confidence that they can do their jobs.

Going forward, it is my strong belief that the United States has a solemn duty to vigorously maintain the classified nature of certain activities and information related to national security. This is an extraordinarily important responsibility of the presidency, and it is one that I will carry out assertively irrespective of any political concern. Consequently, the exceptional circumstances surrounding these memos should not be viewed as an erosion of the strong legal basis for maintaining the classified nature of secret activities. I will always do whatever is necessary to protect the national security of the United States.

This is a time for reflection, not retribution. I respect the strong views and emotions that these issues evoke. We have been through a dark and painful chapter in our history. But at a time of great challenges and disturbing disunity, nothing will be gained by spending our time and energy laying blame for the past. Our national greatness is embedded in America's ability to right its course in concert with our core values, and to move forward with confidence. That is why we must resist the forces that divide us, and instead come together on behalf of our common future.

The United States is a nation of laws. My Administration will always act in accordance with those laws, and with an unshakeable commitment to our ideals. That is why we have released these memos, and that is why we have taken steps to ensure that the actions described within them never take place again.

Here's the statement from Attorney General Eric Holder:

DEPARTMENT OF JUSTICE RELEASES FOUR OFFICE OF LEGAL COUNSEL OPINIONS

In connection with ongoing litigation, the Department of Justice today released four previously undisclosed Office of Legal Counsel ("OLC") opinions - one that OLC issued to the Central Intelligence Agency in August 2002 and three that OLC issued to the CIA in May 2005.

"The President has halted the use of the interrogation techniques described in these opinions, and this administration has made clear from day one that it will not condone torture," said Attorney General Eric Holder. "We are disclosing these memos consistent with our commitment to the rule of law."

Holder also stressed that intelligence community officials who acted reasonably and relied in good faith on authoritative legal advice from the Justice Department that their conduct was lawful, and conformed their conduct to that advice, would not face federal prosecutions for that conduct.

The Attorney General has informed the Central Intelligence Agency that the government would provide legal representation to any employee, at no cost to the employee, in any state or federal judicial or administrative proceeding brought against the employee based on such conduct and would take measures to respond to any proceeding initiated against the employee in any international or foreign tribunal, including appointing counsel to act on the employee's behalf and asserting any available immunities and other defenses in the proceeding itself.

To the extent permissible under federal law, the government will also indemnify any employee for any monetary judgment or penalty ultimately imposed against him for such conduct and will provide representation in congressional investigations.

"It would be unfair to prosecute dedicated men and women working to protect America for conduct that was sanctioned in advance by the Justice Department," Holder said.

After reviewing these opinions, OLC has decided to withdraw them: They no longer represent the views of the Office of Legal Counsel.