Tails (https://tails.boum.org/) is a "live" bootable system. That is, you boot it from DVD, USB, etc. According to the "About" page, it forces all traffic through Tor.
If you booted Tails from a work computer, the IT folk would be able to tell that you shut down the OS and rebooted it some time later, "some time" being the length of your Tails session. They'll also be able to tell that you connected to a Tor node. Those two things together are likely to cause some difficult questions from your bosses if they're noticed.
Can they see exactly what you did? Probably not. There are some attacks on Tor detailed here: https://en.wikipedia.org/wiki/Tor_%28anonymity_network%29#Weaknesses Whether your corporate IT department is up to those I do not know. Probably not. They might, however, try to block Tor, either on general principles or because they noticed activity. Tails claims to be able to circumvent certain kinds of blocking. It is at least plausible that your IT department will notice attempts to circumvent blocking, and quite likely if they've blocked Tor because they observed you using it.
I see that you are in France. I have no idea what the French government thinks of people using Tor, but you should find out before you try it!
Best advice: While at work, do work. While at home, play.