Both fun and funny can be used to describe something (as adjectives).
This cartoon is funny. (Funny describes the cartoon.)
Going to a water park is fun. (Fun describes the activity.)
Compare these sentences:
Susan is a fun girl. (I enjoy myself when I'm with Susan. I have a good time with her)
Susan is a funny girl. (Susan makes me laugh.)
When fun is used as a noun, it means enjoyment or pleasure.
- I had fun at the beach last weekend.
- Your birthday party was lots of fun!
Fun used as a noun, can also be used to talk about someone's good humour and playful behaviour. "Tom's not boring at all, he's loads of fun." 