Politics essay - need halp clarifying congress control over budget

So essentially, as far as I can tell from this book, the way it works is:

- Executive proposes budget
- Both houses review it in their approporiation committees and individually in theory taking into account what is best for their constituents
- Modifications occur (be they through negotiation or otherwise)
- Appropriation bill passed

Am I getting it? The entire essay isn't on it, it's just one of the powers that congress has over the president's office, which is part of what I'm writing about.