They are advantageous roots, and quite normal for tomatoes and many other plants. It's one reason why you can plant tomatoes very deeply and they root up anywhere their stems touch earth. Harmless and normal.

That's 'adventitious' roots....roots originating from an above ground location or from stems, branches, or leaves. (That's what Calliope meant and she's probably smacking herself in the forehead.)

Yes, I was laughing about it about an hour later when it hit me what I said. I thought it didn't sound 'quite' right. Thanks rhizo..........I wouldn't have wanted Marcia to repeat what I said in error.