The working plan for the business are similar to your business hours. These are the hours your business will take appointments. In most cases, it is the same as your providers (employees) working plan.
If your provider's working plan is different, than you change the working plan for the provider in the Users > Providers section. An example of when you would want it to be different is when your Provider works part time, or you have long hours and your provider only works part of the day.