Okay kiddo, so you know how sometimes grown-ups go to school to learn new things or listen to someone talk about interesting ideas?
Well, sometimes there are grown-ups who are really good at teaching or talking about interesting things, and other grown-ups want to hear them talk. So, these really good teachers or speakers go on what's called a lecture circuit.
This means they go from place to place - like different cities, universities, or conferences - and give talks or lectures to different groups of people who are interested in what they have to say.
It's kinda like how the circus or a band goes on tour and travels to different cities to perform. Only instead of performing, these grown-ups are talking and teaching about different subjects.
People who are on the lecture circuit may travel a lot and give talks to different groups of people, but they usually have a lot of experience and knowledge about what they're talking about, so they're really good at it!
Does that make sense, kiddo?