Bills can be introduced in either house, though as noted above, a bill must eventually pass both houses to become law. The exception to this is that bills for raising revenue must originate in the House, and never in the Senate. Committees Both houses of Congress, the House and the Senate, are divided into large groups called Committees, with most committees divided yet again into Subcommittees. Each Committee tends to a general topic in the nation's business, like Finance or the Military. Subcommittees are even more specialized, with one on, for example, Military Nuclear Weapons, and another on Military Pay.
Bills typically concern a specific topic, like raising the pay of soldiers.
Most will, then, fall into a specific sub-committee's area of responsibility. There is a Subcommittee on Pay, Promotion, and Retirement that would consider the pay bill. Once a bill is introduced, it is assigned to a committee. A bill is scheduled to have hearings, at which time witnesses may be called to testify as to why a bill is needed, and sub-committee members ask questions of the witnesses to determine the need or validity of the bill. Once the hearings are held, the members of the subcommittee will then vote on the bill to see if it should proceed further, on to the full committee.