Disk space is the definite amount of bytes of a disk drive. The storage device is server computer's hard drive, but it can also be a USB thumb drive, a CD or DVD, a memory stick/card, or a floppy disk.
Disk space is usually measured in kilobytes (KB), megabytes (MB), gigabytes (GB), or terabytes (TB). For example, a hard drive that is 500 GB is capable of holding 500 Gigabytes of information.
Storage capacity refers to how much disk space one or more storage devices provide. It measures how much data a computer system may contain. For an example, a computer with a 500GB hard drive has a storage capacity of 500 gigabytes. A network server with four 1TB drives has a storage capacity of 4 terabytes.
Storage capacity is often used synonymously with "disk space." However, it refers to overall disk space, rather than free disk space. For example, a hard drive with a storage capacity of 500GB may only have 150MB available if the rest of the disk space is already used up. Therefore, when checking your computer to see if it meets a program's system requirements, make sure you have enough free disk space to install the program. If you need more disk space, you can increase your computer's storage capacity by adding another internal or external hard drive.