An estimate of income and expenses over a defined period; month, quarter, year or three year.
Budgets are an essential part of any planning and operating of a business. Failing to budget very rarely ends well.
Make sure you budget for growth in the business, failing to do so could lead to stagnation and eventual failure.
Budgeting can be done on a simple MS Excel spreadsheet, as well as several apps are available.
The most important thing is to be realistic, face the realities and plan how to take the opportunities offered.