What is it?

Hello everybody,
I have got some questions for you about the above pictures :
1. What is the festivity called ?
2. When is it held this year?
3. In which country is it very well-known?
4. Where do you go to join the festival?
5. What are there in the floatings?
6. Is there a song about it?
7. What time do you float the krathong?
8. Why do you float it ?
9. When did the festival first begin?
10. Who was the famous lady creating the krathong?
Enjoy the festivity!
W.