How to ask professor to explain something again?

I would like to take a different perspective than Buffy:

You were late (maybe even disrupted the course when entering the room) and missed something. Now you want additional time from your teacher to catch up something which happened in the first 10 minutes - which will take ~5-15 minutes of the working time of your teacher. Multiply this by 100 students and 5 courses per week, and you will spot the problem ;-).

Therefore, I would suggest to try everything you can do to catch up on your own. Ask other students. Use books. If you invested >3h without success, you can still write this e-mail explaining what you already understood, where you struggled and at which point you need specific help.

This will show your professor you are really engaged and makes it easy to answer your question within seconds. Maybe (s)he will ask you "just to talk a few minutes after the next lecture" which is also very time effective.

The behavior also depends a bit on your local student-teacher-relationship. In my course, I would not mind if you just approach me after class, you will receive a little (friendly but sarcastic) remark about being late, and get an answer (and I'm happy that someone is trying to learn something).

Perfect question for office hours! Go and wait for your turn to ask.

Yes, it is appropriate, though you will want to apologize for being late. Most professors, good ones anyway, value questions and the students who ask them. If the prof in question holds regular office hours that would be the most appropriate time to ask.

I don't think there is any "special" way to ask. What you suggest seems fine to me.

You can also try to get up to speed on the topic before you meet, using text books and the like. Or discussions with fellow students.

I was once thought to be very smart because I asked a lot of questions. On the other hand, my mother thought I was a "pain" because I asked a lot of questions. But she wasn't a professor.