What is Appropriations Bill?

Legal Definition
An appropriations bill is a bill that appropriates (gives to, sets aside for) money to specific federal government departments, agencies, and programs. The money provides funding for operations, personnel, equipment, and activities. Regular appropriations bills are passed annually, with the funding they provide covering one fiscal year. The fiscal year is the accounting period of the federal government, which runs from October 1 to September 30 of the following year. Appropriations bills are under the jurisdiction of the United States House Committee on Appropriations and the United States Senate Committee on Appropriations. Both Committees have twelve matching subcommittees, each tasked with working on one of the twelve annual regular appropriations bills.

There are three types of appropriations bills: regular appropriations bills, continuing resolutions, and supplemental appropriations bills. Regular appropriations bills are the twelve standard bills that cover the funding for the federal government for one fiscal year and that are supposed to be enacted into law by October 1. If Congress has not enacted the regular appropriations bills by the time, it may pass a continuing resolution, which generally continues the pre-existing appropriations at the same levels as the previous fiscal year (or with minor modifications) for a set amount of time. The third type of appropriations bills are supplemental appropriations bills, which add additional funding above and beyond what was originally appropriated at the beginning of the fiscal year. Supplemental appropriations bills can be used for things like disaster relief.

Appropriations bills are one part of a larger United States budget and spending process. They are preceded in that process by the president's budget proposal, congressional budget resolutions, and the 302(b) allocation. The U.S. Constitution (Article I, section 9, clause 7) states that "No money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law..." This is what gives Congress the power to make these appropriations. The President, however, still has the power to veto appropriations bills.
-- Wikipedia
Legal Definition
When congress uses public money for a specific goal. The bills are voted on every year and must be clarified before being passed. It must be edited until both parties agree on the terms.