Is `DATE` a function?

Hello, Friends,

Use it like a normal function:

playground=# SELECT DATE();
ERROR: function date() does not exist
LINE 1: SELECT DATE();
^
HINT: No function matches the given name and argument types. You
might need to add explicit type casts.

playground=# SELECT DATE('2022-01-13');
date
------------
2022-01-13
(1 row)

Another reason I think this is a function is that other types don't
seem to have the same behavior:

playground=# SELECT integer('123');
ERROR: syntax error at or near "("
LINE 1: SELECT integer('123');
^

The Table 9.33. Date/Time Functions in the documentation
(https://www.postgresql.org/docs/16/functions-datetime.html#FUNCTIONS-DATETIME-TABLE)
doesn't mention this...
If I missed it, where should I find the description? Or maybe it
actually should be in this table?

Thanks in advance.