It supports bits, bytes, kilobytes (KB), megabytes (MB), gigabytes (GB), terabytes (TB), and petabytes (PB).
KB (kilobyte) is 1000 bytes in the SI standard. KiB (kibibyte) is 1024 bytes in the binary standard. Operating systems often use KiB but label it as KB.
1 GB equals 1000 MB in the SI standard, or 1024 MiB in the binary standard used by most operating systems.
1 TB equals 1,000 GB in the SI standard (used by hard drive manufacturers) or 1,024 GiB in the binary standard (used by operating systems).
Hard drive manufacturers use SI units (1 TB = 1,000,000,000,000 bytes). Windows uses binary units (1 TiB = 1,099,511,627,776 bytes), so the drive appears smaller.
A typical smartphone photo is 3-5 MB. So 1 GB holds approximately 200 to 330 photos. RAW photos from a DSLR are 20-40 MB each, so about 25 to 50 per GB.
GB (gigabyte) is 1,000,000,000 bytes (SI standard). GiB (gibibyte) is 1,073,741,824 bytes (binary standard). The difference is about 7.4%.