Can you explain the difference between Share and Assign in MSCRM?

Assigning Records

Assigning records is the act of changing the owner of the record.  Depending on security settings, assigning records may impact who can view or edit the record.  In order to assign records to a new owner, you can either

1. Change the Owner on the record on the form.
2. Click Assign on the Command Bar while viewing a record.
3. Select one or more records from a grid view, and on the Command bar, click Assign.

Assigning records can also trigger workflows, such as a notification that a record has been assigned to you.

Sharing Records

When security settings prevent some users from seeing or editing all records in the Dynamics 365, it may be necessary to share records that require collaboration across teams.  When sharing, you can share the view, edit, assign, or delete rights as long as you have them yourself.  In order to share records,

1. While viewing the record or while selecting one or more records on the grid view, click Share under the ellipsis on the Command Bar.
2. Individually select the rights that the users will have to the shared records OR select Toggleon the left to toggle on/off all rights.
3. Click Share.

The individuals who have rights to see the record are not visible on the record.  In order to see them, you must click Share again on the Command Bar.  From there, you may add or remove rights.