Tim Drake was always destined for something great, his mind and ability to do just about anything he put his mind to made him a prodigy like no one else. But he always wanted something more...enter The Batman.
Tim became obsessed with Batman, and wanted to try and figure out who he was. Batman was aware of this though and led him off course. Depending on which continuity you're in, he either lost his father soon after, or his parents were forced into protective custody and he had to change his identity. Either way, Batman/Bruce Wayne took him in to be Robin soon after.
Of all the Robin's, Time is the most versatile, and easily the most like Batman himself. Even Batman has stated that. He's a genius when it comes to gadgets, computers, martial arts, and more. It is this ability that has allowed him to work both alone and in teams with great effect. Including leading the Teen Titans on numerous occassion, and helping his fellow Robins when they've needed him.
Many believe it's Tim who will inevitably become Batman once Bruce is gone, even moreso than Dick Grayson. At the rate he's going? It's only a matter of time.