Microsoft has a series of demo pages that go ‘step by step’ through the main features in Teams.
https://Teamsdemo.office.com is the demo to start with.
It explains the main elements of Teams including channels, members, posts etc.
All the demos are focused on Teams not Teams Free but is OK for free users.
There are other demos that only get mentioned after the main one has completed.
Chats and Meetings
https://teamsdemo.office.com/ChatsAndMeetings/index.html#/ is especially good for anyone unfamiliar with the voice and video calling options.
We’d like to see a really basic demo about simple audio and video calling. Something aimed at people who haven’t used computer calling much (yes, there are some out there!) and need to go through the basics like mute, video on/off, text messaging etc.
Tips and Tricks
Once you’ve got the basics, have a look at Microsoft’s ‘Tips and Tricks’ demo.
Teams for Mobile
As a fairly new service, Teams was developed with mobile access firmly in mind.
https://teamsdemo.office.com/mobile/index.html#/ goes through the choices for using on iPhone, iPad and Android.