Is there a word for numbers and letters, but not punctuation, etc?
An alphanumeric character is one which is either alphabetic or numeric — that is, either a letter or a digit. As a noun, we can talk about alphanumerics for the collection of them, as I do here in this answer.
The term alphanumeric does not include punctuation, symbols, combining characters (like diacritics), spacing characters, or control characters.