Usually, the professors ask, ", right?" or other questions which very clearly seem to be rhetorical. If no one says anything for a few moments, they'll move on with the lecture as if nothing happened.
It's hard to judge without being there, but this sounds to me like the instructor is giving a pause to see if there are any questions on what they've just discussed before they move on.
From a US perspective, if they look right at you and you feel like you're following and understanding things well, feel free to nod, give a thumbs up, whatever feels to you like a comfortable response to affirm that you understand. This isn't to test or evaluate your knowledge, it's a self-evaluation to the instructor to gauge whether they're being clear, whether they're moving too fast, whether they need to restate or rephrase something they've said. As pointed out in the comments, the appropriate gesture can be culturally dependent; I think a head nod is pretty safe, but I can't say for certain. If you have a question, though, it would be a good time to ask it/indicate you have a question to ask by raising your hand or whatever signal is typical in your classroom.
If the professor looks at a specific individual (for example, you), I don't think they are necessarily intending to pick on that person specifically, but they may be looking for a representative response or maybe they noticed that person looked a bit puzzled earlier and they're just checking in. It's part of interacting with an audience that some people are more natural at than others.