Short answer
After you connect your calendar, HubSpot's KB says the dedicated calendar view lets you review past meetings, prepare for upcoming ones, and schedule new meetings in one place. It appears as Calendar in the Sales menu. Without a connected calendar, the page shows a Connect calendar prompt.
1. Before connecting
My demo login has no calendar connected, so my demo portal shows the prompt.

2. Related
Syncing tasks to calendar and the sales workspace.