This article outlines how to share your Google Calendar with someone else. It will also outline the different permissions available and what they do.
1) Open Google Calendar.
2) Hover over the calendar which is intended to be shared and click on the 3 vertical dots > "Settings and sharing".
3) In the calendar settings, navigate to "Share with specific people" >click on "Add people".
4) Enter the email address of the person who you intend to share your calendar with.
5) Next, click on the downward arrow underneath the "Add email or name" field to apply the desired permissions.
6) When happy, click "Send".
Google Calendar Permissions
See only free / busy: Recipients will only be able to see when you have appointments but not what those appointments entail.
See all event details: Recipients will be able to see everything on your calendar but won't be able to make changes.
Make Changes to events: Recipients will be able to see everything on your calendar and will be able to make changes.
Makes changes and manage sharing: Recipients will be able to see everything on your calendar, make changes, and invite more people to see your calendar.