Partitioning your hard drive is simple splitting it up into 2, 3 or more hard drives, once it is done your computer will see them as separate hard drives. There are several reasons as to why you would want to do this, one is if you split a drive into say drive c and drive d, you can save all your data on drive d. this makes backing it up easier as its all in one place and you can get into the habit of storing anything you want to save in you “data” drive. If you put your operating system on drive c if you need to re-install it you can do this without destroying your data on drive d.
Another reason you may want to partition a hard drive is to have multiple operating systems. Each operating system has its own settings and programs and runs almost as a separate computer, you could have one system set up for general computing with all your “normal” programs installed and you could have another system set up specifically for music programs, this then need not have any Internet browsers email or anti virus software installed and could use all or your machines computing power on the music and recording software without having lots of necessary services running in the back ground such as email and anti virus. You would also have less distractions!