Candid: The person/people are unaware that they are being photographed. The picture is taken without causing any distraction to the subject (like preparation and trying not to surprise them) while the subject is in motion. It can be beautiful to catch an image like that at the perfect moment. Candid shots are very good
Posed: The person/people are aware of the photograph being taken. They follow instructions the photographer gives them (certain poses, expressions, mood, etc.) Posed shots are planned, so they might not be as beautiful as candid ones.
Hope this helps :)