Explanation:

Box 1: Base only
Box 2: Base and Attach
Base licenses and cost savings opportunities for "attach" licenses
Microsoft provides a cost-effective way for a single Dynamics 365 user to obtain full user licensing for multiple products. Licenses for products that provide core business functionality qualify as base licenses. (See the table below.) Each has one or more additional applications that are frequently used by people in the same roles and that qualify as attach licenses for that user. (These are sometimes referred to as subsequent qualifying applications.) To take advantage of the special attach license pricing:
1. Buy the first base user license at standard pricing.
2. Review which attach licenses are available for that base. (See the qualifying products for each base license below.)
3. Buy attach licenses for the same user at an attach license price. You may buy as many attach licenses as are available for that base license.
Every full user must have a base license, though the base licenses don't need to be for the same product. (For instance, an attach license for Customer Service Professional is available both for a user with a Finance base and another with a Commerce base.) Base applications and their qualifying products for attach licensing Table Description automatically generated

Reference: https://go.microsoft.com/fwlink/p/?LinkId=866544
https://docs.microsoft.com/en-us/dynamics365/get-started/team-members-license