If you know of Skype or Skype for Business then you know about Microsoft Teams.
If you have been instructed to come here to download teams what you need to know is 000PC PTY LTD is not supplying Microsoft Teams just supplying the grey box in the top right that will take you to Microsoft.com do download the latest version.
Once you have installed Teams on your device you can make an account if you don't already have one.
Joining as a GUEST is also available and this can be prompted when selecting JOIN MEETING from the invite email you were sent and selected "Join as GUEST"
this page will change as required to be more clear and help full over time.