Microsoft Teams is a really powerful tool that has blossomed during the Covid-19 lockdown period, allowing many colleagues who are isolated in their own homes to keep in touch and collaborate with one another remotely.
The product is very feature rich (and getting ever more so) so can be a little daunting when starting out. One often missed feature of Teams is that there is a wealth of help and training built right into the application itself on both the desktop (Windows and OS X) and web based versions.
You can find the Help at the bottom left of the Teams application, on the web version it is between the Apps and Download buttons.
Clicking on the icon will take you to the Help part of Teams, starting with a list of common topics. What you see here is partially related to your Office 365 tenancy, for example in the picture below there are items relating to Remote Learning as this was taken from an Education version.
There are also a wide range of bite sized training videos available right from the same place and these cover everything from getting started through to collaboration and managing the activity feed.
All in all these are a really good way to get started with Teams.