In calendar there’s a button on the ribbon to share your calendar, it looks like this:

Click on it and a new window will open where you can send a calendar sharing invitation to someone. You have a few options for how much detail you show, by default its ‘Availability Only’ which is already the case for everyone.

‘Limited details’ will show the subject of the appointments/meetings but not location or attendees.

'Full details' show everything including any message inside the calendar item (for example a meeting link)

Here’s an example of sending a sharing invite to include full details. Make sure you fill in the ‘To…’ box and note you can send the share invite to more than one person at a time.

If you have personal reminders or anything in your calendar that you’d rather keep private then marking items as private is very simple. If you right click on an item you’ll see an the ‘Private’ option which will make it so only you can see those items even if someone has full access to your calendar.