See More Details from the Event Preview

From your calendar, click an event to see a preview of up to 10 fields. Previously, you could see up to four fields.

Where: This change applies to Lightning Experience and all versions of the Salesforce app in Essentials, Professional, Enterprise, Performance, Unlimited, and Developer editions.

Why: Reps can view more event information directly from the calendar home page without having to open events to see important details.

Calendar view, showing an event preview with location, contact,related to, and other details