When a user no longer works or volunteers for your organisation you will want to remove them from the system inline with your data retention policies or at minimum to keep within your license allocation.
Suspending a user prevents the user from logging into the system, however their account is still available within the password. A suspended user can be unsuspended at any time and their access can be resumed immediately. This user still appears in all reports and can be added to different groups and managed as a standard user, except they are unable to login. This user still counts towards your license total.
Deleting a user will remove the users email, username and preferences. They will be unenrolled from courses and their grades will be removed. It will remove as much data as possible from the platform. There are exceptions such as forum posts or wiki posts which will not be removed as other users may be dependant upon that data. Additionally Course Completions and SCORM records will remain attached to the deleted account for compliance purposes. The user will never be able to login again and the account is archived for legacy reporting. These users do not count towards your license allocation. Deleting a user will leave their firstname, lastname and key information available for the platform inline with data integrity practices.