It's a hobby if you go to "shows" and talk to other hobbiests about it. A pile of stamps in a shoebox in someone's attic is a collection. A well presented book

It's a hobby if you go to "shows" and talk to other hobbiests about it. A pile of stamps in a shoebox in someone's attic is a collection. A well presented book of stamps that is taken to shows, shown, discussed, etc. That person is a hobbiest.