The boot hard drive is the first hard disk installed in your PC which we load the opearting system (Windows) on, it also holds all your software installation files.
Choosing a 'Solid State Drive' option will have a dramatically positive impact on the speed of your computer as these drives are able to read data at much faster speeds than traditional hard drives.
If you select a SSD we strongly recommend chosing a 2nd hard drive for your data storage requirements.