The C: drive on a Windows PC is the main storage drive for the operating system and installed programs. It is often referred to as the "system drive" because it stores important system files, as well as user data and installed programs. The C: drive is usually partitioned and formatted as a local hard drive when the operating system is installed, and it is typically the largest storage drive on a PC. You can think of it as a large filing cabinet that stores all of your important files and documents, as well as the programs and software you use on your computer.