"Public" places are places where people who you don't know can see what you're doing. Some public places include:
- on the street
- at school
There are other places which might be considered public or private depending on the situation. For example, someone else's house is private for them, but might be public for you. On the other hand, if it's a close friend's house, you might not think of it as being public.
Describe things that you do in front of strangers as "in public":
I'm a decent singer, but I hate singing in public.