brutal_lobster

man 5 shadow
man 3 crypt

If salt is a character string starting with the characters
"$id$" followed by a string terminated by "$":

$id$salt$encrypted

then instead of using the DES machine, id identifies the
encryption method used and this then determines how the rest
of the password string is interpreted. The following values
of id are supported:

ID | Method
─────────────────────────────────────────────────────────
1 | MD5
2a | Blowfish (not in mainline glibc; added in some
| Linux distributions)
5 | SHA-256 (since glibc 2.7)
6 | SHA-512 (since glibc 2.7)

So $5$salt$encrypted is an SHA-256 encoded password and
$6$salt$encrypted is an SHA-512 encoded one.