Short answer
HubSpot's KB: a tracking URL needs a campaign name, used in several reports. The Source you pick decides how visits are categorized in traffic analytics. UTM term is optional and tracks pay-per-click keywords.
1. In HubSpot
The relevant screen in my demo portal.

2. Worth knowing
Connecting Google Ads in the ads tool gives more data where the ad type is supported.
3. Related
UTM settings and ads data mismatches.