Hashing (SHA-256)
SHA-256 is the specific hash function Bitcoin uses; it always produces a 256-bit (64 hex character) output.
In depth
SHA stands for Secure Hash Algorithm and the 256 is the output size. Bitcoin miners run SHA-256 trillions of times per second searching for a block hash that starts with enough zeros. Other networks use different functions — Ethereum uses Keccak-256 — but the principle is identical.
Why it matters
When you see a transaction ID or block hash on an explorer, you are looking at a SHA-256 output.