Non-Segwit Output Script Descriptors.

Defines how descriptors write the three original standard types: pay to public key, pay to public key hash, and pay to script hash.

Before segwit there were three main standard formats: paying straight to a public key, to a hash of a public key, or to a hash of a script. This BIP lets a descriptor, the text that records which addresses a wallet uses, name each of them.