Explanation

Box 1: delete a row from Table1
Members of the db_datawriter fixed database role can add, delete, or change data in all user tables.
Box 2: db_datareader
Members of the db_datareader fixed database role can read all data from all user tables.
Reference:
https://docs.microsoft.com/en-us/sql/relational-databases/security/authentication-access/database-level-roles