MD5
In plain terms
An old, now-insecure hash function.
Going deeper
MD5 produces a 128-bit hash but is broken for security because collisions can be engineered. It survives only for non-security checksums.
Under the hood
Cryptographically broken (collision attacks); never use for security, only for quick non-adversarial checks.
Examples
Legacy checksums, file deduplication (non-security), deprecated hashing.
Think of it like...
Like an old lock whose key everyone now knows how to copy.