I am trying to find out how budgets help with planning, coordinating activities, communication, and evaluating performance. My book is very vague - please help. Thanks!

Budgets are projections for the following year. They are a measurement on how well you know the company. Then through the month actuals are measured against the budget to see if the company is performing as projected. Budgets are usually calculated by the years actuals with the assumptions and % increases and/or decreases depending on the individual company goals