What is a budget? (Need 2 sentences or more)

For this case, we have that by definition, a budget refers to:

An advance calculation of the cost of a work or a service.

For example:

"I asked the mechanic for the repair budget for my vehicle".

As another definition we have:

A set of expenses and income expected for a certain period of time. In the same way, it can be defined as a plan of operations and resources of a company.