What are these little bits on my Basil?

I have 2 basil plants in separate rooms, one I grew from seeds, one from the supermarket.

My seed one is going fine, no sign of anything wrong. But my supermarket one has these ‘bits’ on it. They didn’t appear until a month or so from having it. I feel as though I have had Basil plants from a supermarket have these before.

Is this a parasite or a predator, like an aphid?