One definition for collection is; a group of objects or works to be seen, studied, or kept together.
Whether you collect stamps, coins, or baseball cards, the collection is typically something meaningful to the collector or stored away as an investment for the future.
What do I collect? Vintage ceramic ashtrays (I don’t smoke, but I love the sculptural aspects of them), souvenirs from Florida, and Mexican bird pottery.
Check out this Country Living slideshow for a look at the usual, and not so usual, things people collect; it might inspire you to start your own!