What commerce covers
Commerce is broader than just trade (buying and selling). It also includes the "aids to trade" -- services that make trade possible and efficient: banking (finance), insurance (risk protection), transport (moving goods), warehousing (storage), advertising (informing buyers), and communication (coordinating business activity).
Example 1: A trader needs to store unsold goods safely, insure them against fire damage, and transport them to a distant market. Name the three aids to trade involved.
Warehousing (storing the goods), insurance (protecting against fire damage risk), and transport (moving the goods to market) -- each is a distinct aid to trade supporting the underlying buying-and-selling activity.
Classifying occupations
Occupations are broadly classified as direct services (providing a service straight to the public, like teaching, medicine, or hairdressing) or commerce/trade-related occupations (buying, selling, and the aids to trade, like a shopkeeper, banker, or insurance agent). This distinction helps explain how different parts of an economy contribute to getting goods and services from producers to the people who need them.