The Moodle calendar can display site, course, group, user and category events in addition to assignment and quiz deadlines, chat times and other course events.
Your calendar can be accessed from your My Pages area with a list of upcoming events in the left hand side of the page.
You can see an event in more detail by hovering over it:
To see your calendar in full, either click on the Month link eg (October 2018) or click Go to calendar in upcoming events.
You can then click New event if you wish to add your own event.
Give your event a title, and set the date and time and then click Save
Your event will then appear on the calendar as a user event.
You may also see a calendar and / or the upcoming events in your individual module pages if they have been added and they are used in the same way.