One of the last options of the Database Maintenance Plan Wizard is to perform a history cleanup.
The MSDB database stores a lot of information regarding the activities performed on your database. It contains information about your job execution, plan execution information, scheduled job execution information, backup history, etc. After a while this can cause your MSDB to grow considerably, while not retaining information relevant to your current operations.
Setting values for the history cleanup allows you to perform cleanup on one or more types of history. You can also specify how long to retain data in the history so you have a rolling window, or purge all history if it isn’t needed.
It’s important to clean up this data from time to time to keep your tasks working efficiently.
For more information on this task, see the History Cleanup section of https://docs.microsoft.com/en-us/sql/relational-databases/maintenance-plans/use-the-maintenance-plan-wizard.