Very basic question...please define "sucker"

[texasjack]

I've been growing for several years. Some years I've pruned, sometimes heavily sometime sparingly, some years not at all except for diseased areas. Frankly I haven't seen dramatic differences in productivity.....I recognize this is a non scientific conclusion with so many other varibles.

After reading up on pruning here and other sources I've become confused by the terminology used.

What exactly is a "sucker"? My plants have a) mostly vertical members..."stems" b) mostly horizontal members that grow at approx 90 degrees to the "stems" and produce only foliage and c) members that grow out of the "stems" at angles of 30-45 degrees upward from the "stem". Pollinated blossoms and fruit generally occur at or near this ★★★★★★★★.

OK...please straighten me out on the correct terminology and explain what gets cut off. I do not subscribe to the idea of cutting off some of the vertical "stems", but I might be persauded.

Extra Credit Question.....If you do prune do you cut very close to the "stem" or do you leave 1" or so that later dries up and falls off by itself ?

Thanks

Texas Jack