Yes, a vocal song can have an instrumental version, in which the lyrics are missing. Instrumental can mean two things:
- a "karaoke" version with the vocals removed; or
- a song which was written without vocals in the first place.
Incidentally, some people insist a "song" must have vocals. These people use the word "piece" to refer to a song without singing, which is traditional and etymologically correct. In common use, people use "song" to refer to instrumental songs as well.
How is this relevant? If you're talking about an instrumental metal group or the instrumental version of a pop song, people say "instrumental song"; if you're talking about classical music with no singing, people usually say "piece".
A "backing track" is a track without all the instruments for a musician to play over, which is somewhat different. A guitarist may have a backing track consisting of bass and drums that they play over.