If you've gotten a full, non-academic copy, then you are licensed to install it onto up to three computers AS LONG as no more than one of the three computers is running the program at the same time.
Thus you can install it on your home desktop, your work computer and a laptop as long as you are only running it on one of the three computers at a time. You are NOT allowed to install it on three work computers or you and your assistant's computer if you're both going to run it.
If you have gotten an academic copy, then you are only licensed to install it on a single computer at any one time.