Definitely 'comping'.
Be it with first positions chords and strumming them, or with 4 notes chords in a jazz standard.
Anyone can play solos, but a great guitarist (IMHO) shows in the way he outlines a singer's or a soloist's performance. That's what sets Van Halen apart from a lot of other guitarists. He can play those amazing solos, but even without them, the song is beautifully crafted with his rhythm guitar. There's also Jim Hall in that category, or Joe Pass.
Also, that's comping that will make you get a gig or not. A singer doesn't care about you phrygian licks or your string skipping skills. He wants his group to sound good. And that's the groove that makes it sound good.