Overview of Funding Mechanisms in the Federal Budget Process, and Selected Examples [Updated February 5, 2021] [open pdf - 1MB]
From the Summary: "Every year, Congress considers numerous pieces of legislation that would create or modify federal government programs and activities. The variety of approaches used across the federal budget to fund these programs and activities involve different timelines for budgetary decisionmaking, and different processes within Congress to make those decisions. How a particular funding mechanism is structured requires tradeoffs between the frequency of congressional review and the predictability of funding for the program. The purpose of this report is to explain these approaches, illustrating them with examples."
CRS Report for Congress, R44582
Congressional Research Service: https://crsreports.congress.gov/