Taking attendance in meetings is a useful feature to be able to monitor who attended your meeting or event. You can check which staff members attended training, or check who attended your webinar to help with follow-up activities. For education institutions, you can check if students have attended classes when learning remotely.
Within Microsoft Teams, you can track attendance of your meetings. After you have scheduled and finished your meeting, you can click back into the meeting invite in your Teams calendar, and you will see a copy of an attendance report which is automatically generated when your meeting starts:

The attendance report is an Excel file, which you can download to your computer. It will provide details of the meeting, who attended, their role and if they left and re-joined:

If you have external participants join your Teams meeting, you cannot see their email address, but you can see their name and the time they joined and/or left the meeting.
You can also view your attendance in a tab in your Teams Meeting calendar invite. This will show you how many people attended, the duration and the average attendance time:

If you want to check attendance during your meeting, you can click on the three dots in the participants pane and choose download attendance list. You will need to download this again after the meeting to get a complete list.

The attendance report is created automatically by Teams and happens when you create a Teams meeting, Webinar or a Live Event. For more information about the types of meetings in Teams, check out my previous blog: What’s the difference between a Teams Meeting, Webinar and Live Event?