Different address prefixes for different address types / network combinations
Different networks use different address prefixes.
In Bitcoin mainnet:

P2PKH addresses: 1...
P2SH addresses 3...
P2WSH and P2WPKH addresses: bc1q...
P2TR addresses: bc1p... (see BIP 341)

In Bitcoin testnet and signet (see BIP 325):

P2PKH addresses: m... or n...
P2SH addresses: 2...
P2WSH and P2WPKH addresses: tb1q...
P2TR addresses: tb1p...

Bitcoin Core's regtest network:

P2PKH addresses: m... or n...
P2SH addresses: 2...
P2WSH and P2WPKH addresses: bcrt1q...
P2TR addresses: bcrt1p...

See also https://en.bitcoin.it/wiki/List_of_address_prefixes