Known for its versatility and durability, cast iron skillets are the kitchen's most universal tool.  You can use your cast iron like any other pan you might have but with certain restrictions.   Cast iron is multipurpose in that you can use it on the stove top as well as the oven.  It can be used for frying, stews and soup, stir fry, baking, and some great blackened steaks.
The trouble with cast iron, is it takes a little effort to maintain.  But the effort is well worth it.  Here are a few things to keep in mind:  

*Seasoning: This term simply means there is a layer of lubricated residue on the surface of the skillet that flavors food while resisting adhesion thus creating a non-stick, but flavorful, surface.  It sounds gross, but is's actually awesome.  

*Do you have to season? : Some pans come pre-seasoned and it should say this on the label if purchasing new.  If purchasing a pan at a garage sale or thrift store, it’s best to assume you'll need to season it yourself especially if the surface is rusty and bumpy.  

*How to season: There are many ways to season, here is one way.   First, give it a good scouring by scrubbing it with kosher salt and a damp sponge then thoroughly rinse the pan.  Next, completely dry the pan in a hot oven.  After its dried and cooled, poor a tablespoon of unsaturated oil (I use canola) in the skillet and rub it all over with paper towels.  With fresh paper towels, remove any excess.  Then, place the oiled pan upside down in a 450 degree oven and bake for an hour.   Remove from the oven (making sure to use potholders!) and allow to cool.  Repeat the process up to 5 times until you achieve that shiny, classic, cast iron finish.  Repeat this lengthy process whenever your skillet need to be re-seasoned, which isn't that often if you clean it properly.

*How to clean: If seasoned well, all you'll need to do is give your skillet a good rinse then completely dry the skillet in the oven.  Do NOT let your skillet soak.  And, please, do NOT put it in the dishwasher.   If there are stubborn bits stuck to the skillet, heat it with kosher salt and oil, and scrub at the bits with paper towels clutched inside tongs.

While cast iron is multipurpose, it cannot be used efficiently on glass top stoves due to the inability to transfer heat.  It should never be used in a microwave own.

Cast iron can add up to 20 times the amount of iron into your food is great for people with iron deficiencies.  You can cook with less oil in cast iron.  The non-stick surface of a well-seasoned piece is almost as effective as effective as the non-stick pan for use without the concerns of introducing chemicals from the coating into your food.  Cooking acidic dishes (tomatoes) might cause a weird taste due to a reaction with the iron.

Why cook with cast iron?   The benefit of using a cast iron pan is that it gets very hot and stays hot.  Unlike thinner pans, the heat level doesn’t fluctuate in a cast iron.  This makes it an ideal choice for foods that need high heat.  Meats that need a sear but should be scorched, like steak, or roasts that should be browned before braising, perform beautifully in a cast iron.