It's heavy, so it retains more heat as you add stuff to it. The heat also spreads more evenly. It can also go in the oven.
There are special instructions for the first time you use it. I don't know what they are, look it up elsewhere.
Avoid cooking tomatoes or other acidic food unless you know what you're doing. It can rust the pan.
Wash the same day. If it's hard to wash add a bit of salt and scrub. Then immediately dry with towel, wipe the top with oil and heat it on a low burner for 10 min. If you don't do this it will rust.