The idea of an xpub originates from BIP32, the place it denotes an prolonged public key, from which a number of baby keys could be derived.
On the time of BIP32, there was actually just one deal with sort generally used, pay-to-pubkey-hash (P2PKH). Thus, BIP32 have been generally understood to suggest a sequence of derived P2PKH addresses.
After segwit, when different deal with sorts got here in frequent use, like P2SH-P2WPKH and P2WPKH, individuals wanted a technique to convey “a BIP32 prolonged public key, however the derived addresses are P2SH-P2WPKH”. This turned the ypub scheme outlined in BIP49 for P2SH-P2WPKH, and later the zpub scheme in BIP84 for P2WPKH. They include the very same data as a BIP32 prolonged public key, however with a unique prefix to indicate the corresponding deal with sort. Varied different variants have been outlined and adopted by some software program, e.g. Zpub for P2WSH, however not standardized by the BIP course of so far as I do know.
Different software program by no means adopted ypub/zpub/Zpub/…, because the persevering with want for brand spanking new prefixes doesn’t scale effectively, and the notion of making an attempt to pack all deal with derivation data right into a single key string additionally simply would not work for extra complicated constructions like multisig. For instance, within the newer output descriptors (BIP380) commonplace, xpub is at all times used, however one would use wpkh(xpub...) to point a P2WPKH deal with sort.
So far as I do know, there is no such thing as a *pub-like commonplace for P2TR but, and for my part there shouldn’t be. It’s a lot clearer to convey deal with sort data outdoors of key strings.
Disclaimer: I am the writer of BIP32, and co-author of BIP380.
