After a bill is introduced on the House or Senate floor, it is referred to the committee of jurisdiction (the committee charged with reviewing measures in the area of law or policy with which the bill is concerned). The committee of referral most often sends the measure to its specialized subcommittee(s) for study, hearings, revisions and approval.
For most bills, the committee or subcommittee fails to take further action on the referred bill, effectively "killing" the measure at this point. Occasionally, a committee will report a measure "unfavorably," with explicit recommendations against its passage, or it will report a bill "without recommendation," which has the same effect as an unfavorable report.
If the bill passes the subcommittee with a favorable vote, it is sent back to the full committee for further consideration, hearings, amendment and vote.