Track totally depends on what you decide to do! You can either run long distance (miles), mid-distance (400 meter), or sprinting (100 and 200 meter). And then there's jumping (which includes pole vaulting). Or you can be a thrower (which means you throw objects around)! Each section has different workouts, so their practices never really end at the same time. You can research each of the sections and figure out which one you want to do. All of them will help you get in shape. And as far as getting faster goes, you have to decide what kind of fast you want. Long distance will help you run miles in very short amounts of time. These races can last a couple of minutes. Sprinting will help you run very short distances in incredibly short amounts of time. These races last a couple of seconds.
Tracks usually require speed and more speed. The intervals for track are generally shorter and faster (300s and 400s) and the races are also a lot faster. The time period of the practise will depend on your coach and if you are a stronger faster person.