Deciding on things like hobbies for your character is all part of making them a well-rounded person who will come to life in your shared alternate reality. Even trivia like favourite foods or colours can help develop him into someone who is 'real' to you... and when it comes to hobbies and interests... well, they are what often define YOU as an interesting person, so why not your character?
This product is just something to help you start thinking, a list of an hundred 'modern' hobbies that your character might spend his leisure time on. Some might even prove an advantage in the reality of the game world, others may merely provide topics of casual conversation. A character who, for example, enjoys car restoration may be at less of a loss when his car breaks down that his fellow party member who spends his spare time playing rugby or poker... but when there's a gang of crooks to infiltrate, that poker-player might come into his own as he joins a back-room game several gang members are known to attend.
If you are serious about role-playing and developing believeable characters who just might exist somewhere, this is a resource that you may find helpful.