"Tails" (which stands for: The Amnesic Incognito Live System) is an open-source OS entirely built around privacy.

It  is portable: it must be installed in a USB stick (minimum 8GB) and can  be used on any computer without replacing its own OS: it's enough to  boot the computer from the USB stick instead of from the hard disk.

Unlike  all 'normal' OS (which, writing data on hard disks, remember everything  - including the data that one permanently deletes, as long as they are  not overwritten multiple times) Tails forgets everything except the data  and settings that one explicitly wants it to remember (these are saved  in the Persistent Volume, which can be configured individually).

In  fact, Tails does not use the hard disk but only the computer memory  (RAM). Every time Tails is switched off, everything is forgotten: apart  from the Persistent Volume, Tails starts always from scratch, as if it  was the first time it was ever used.

Every  Internet connection in Tails is forced through the Tor network: in this  way your entire system becomes anonymous, not only your browser. In  other OS, even while using the Tor browser, other applications connect  to the Internet independently from Tor and your anonymity can be  compromised.

Tails  has interesting security features that you'll discover while using it.  For example, it prevents the computer from reading any USB inserted  while Tails is sleeping or the user is logged out. This is important  because a skilled adversary could gain access to your computer by  installing malicious software via a USB overriding the suspended status.  In this way, this possibility is prevented.

Additional  software is extremely limited in Tails; it can be extremely difficult  or even impossible to install it; and it can compromise the security of  the system. In this sense, apart from some specific additional software  that will be suggested in the course and will be easy to install, Tails  should be considered as a 'closed' OS: this guarantees maximum privacy  and security. However, Tails comes with a lot of secure software  pre-installed.

As  one soon discovers, Tails makes it very easy to do things (in  particular related to privacy and security) which in other OS are very  difficult or even impossible to do. On the other hand, for security  reasons, in Tails it can be very difficult or even impossible to do  things (such as a Zoom meeting for example, or a simple screencast with  audio) which in other OS are banal to do. This is why, in my opinion, it  should be used in addition to another OS, not instead of it.

More info on Tails can be found on the links above.