What is 2³⁰, and what unit does it define?

1073741824 — one gibibyte (GiB): 1024³ bytes ≈ 1.07 billion.

The story: a pair of dice rest beside a board game and a toy car; then a dove perches on a capering narr (jester).

2³⁰ = 1,073,741,824 bytes is the binary "gigabyte" (GiB). This is why a drive sold as "1 TB" (10¹² bytes) shows up as ~931 GiB in an OS that counts in powers of 2 — the decimal-vs-binary gap widens to ~7% by the giga step. Remember it as "1.07 billion".