President Obama on Wednesday asserted executive privilege over Fast and Furious documents just as a House panel prepared to push ahead with a contempt vote against Attorney General Eric Holder.

Here's what the president's action means:

-- Executive privilege allows Obama to withhold from Congress documents revealing internal communications and decision-making of the executive branch of government that he believes should remain confidential.

-- A subpoena by Congress cannot override claims of executive privilege. However, the privilege is considered "qualified" and "not absolute," meaning it can be challenged and overturned in the courts, according to the Congressional Research Service.

During Wednesday's hearing, Rep. Dennis Kucinich, D-Ohio, suggested to chairman of the House Oversight and Government Reform Committee, Rep. Darrell Issa, R-Calif., that the dispute be resolved by the courts before Congress proceeded with a contempt vote. But Issa said the committee is "concurrently evaluating" the executive privilege claim and trying to get a "log" of executive privilege assertions from the White House. He also said the letter he received claiming executive privilege, which was from Deputy Attorney General James Cole, was not sufficient. "Only the president can do it," Issa said. "A letter saying the president has done it is not sufficient."

-- Historically, a challenge of executive privilege rarely reaches the courts. The majority of disputes over access to information have been resolved through political negotiations.

"While reviewing courts have expressed reluctance to balance executive privilege claims against a congressional demand for information, they have acknowledged they will do so if the political branches have tried in good faith but failed to reach an accommodation," according to CRS.

-- The idea of executive privilege is not explicitly mentioned in the U.S. Constitution, but the Supreme Court ruled it to be part of the "separation of powers" doctrine.

-- This is the first time President Obama has asserted executive privilege. Presidents Richard Nixon, George W. Bush and Bill Clinton all resorted to using executive privilege during their administrations. The practice has been used 24 times since President Ronald Reagan to protect the confidentiality of information.