Wall Fish TankA place to live for your favorite pet

Like the title says, I'm new to fish tanks. I only had a little fish tank many years ago, but besides that I don't know much about fish tanks.

If I were to buy a fish tank for my living room, what would I have to pay attention to? Does it matter if I buy a saltwater fish tank or a freshwater fish tank? I think that might be a good point to start.

Any help is greatly appreciated.