Hackathon

Can anyone tell me how hackathons are helpful and when I should take part if I know a bit of coding or when I am given an ample amount of time to coding.??? I also would like to know some prominent hackathons contest names and where to find them??? I saw one of the IIITD students who took part in an IITD hackathon. Can I take part if I am from tier 3 College from another state like Kolkata????