What is a hash?

A hash is the result of applying a hash function to data, representing a fixed-length sequence of bytes or numbers that uniquely (as much as possible) identifies the original data.

Hashes are used for quick lookup, integrity verification, data comparison, and in cryptography. For example, in Go, you can use the crypto/sha256 package to compute a SHA-256 hash:

import (
    "crypto/sha256"
    "fmt"
)

func main() {
    data := []byte("example data")
    hash := sha256.Sum256(data)
    fmt.Printf("Hash: %x\n", hash)
}

Hash functions should be deterministic, fast, and minimize collisions (different data should produce different hashes).