If you are using a Mac, you might be tempted to stay away from any other operating system. Since the Mac is so easy to use and has a nice user interface, why would you bother using anything else?
For the most part, you are right. But if you are working for a company that runs Windows or Ubuntu and you still want to use your Mac, you can do so by running it on a virtual machine. This way, you can have the cake and eat it too. The virtual machine allows you to run any operating system and not have it affect your Mac.
There are many virtualization software on the market. Some are free and some are commercial. The one you choose depends on your preference. For most cases, any of them will work for whatever you might be doing.