Impeachment is the political equivalent of an indictment - being sent for trial. If President Clinton - as widely expected - is impeached in the House of Representatives today, it will then be up to the Senate to hold a trial early next year on the impeachment charges. Dates of January 6th or 7th - when the Congress elected in mid-term elections last month takes its seats - have been mentioned as the likely beginning.
An impeachment vote by a majority of the 435-member House would not remove Mr Clinton from office. Only the 100-member Senate has the power to conduct a trial on the charges, convict the President and remove him from office. However the impeachment vote in the House will have no effect on his powers as President.
If the Senate were to find him guilty by a two-thirds majority of one or more of the impeachment charges, he would be liable to "removal from office", according to Article One of the constitution. Some experts have argued that a separate vote would have to be taken to expel the President from office.
In the only trial so far of a president, that of Andrew Johnson in 1868, he was saved from conviction by one vote.
At any time during the Senate trial, it can be stopped by a simple majority vote. The Senators could then consider a lesser punishment such as censure - a firm rebuke for bad behaviour with no legal consequences.
No time limit is set and some standard courtroom proceedings, such as the calling of witnesses, would be followed. The Senate could by majority vote stop the trial at any time - or fail to convict Mr Clinton. The constitution limits action to removal from office or removal from office and prohibition against holding any future offices of public trust.
If the Senate proceeds with a trial, it would be presided over by Chief Justice William Rehnquist. He is an expert on the impeachment process, and has even written a book on the subject. A Washington colleague half-jokingly described the momentous events taking place this weekend as a sort of a "dream come true" for Justice Rehnquist.