Contact Store is updated on Contact card to help you record the Store they come from.
Stores is an add-on to help you track multiple channels for sales, each with an identity. Store One might be your primary, while Store Two has a different address for printing.
Store Categories automate accounting, Cash Drawers tally deposits, and many Connect options like Ecwid, HubSpot, Shopify, or WooCommerce let you assign to keep track.