An ales is a type of beer that is fermented at the top of a hill, in a cave, and with a very specific type of yeast. It's like a normal beer, but with more hops.
Here is a subpage about British Bitter and Saison.
Or, if you're feeling adventurous, check out American Ales.
Lagers are the opposite of ales, in that they are fermented at the bottom of a lake, in a shed, and with less hops. They are like normal beers, but with less character.
For the really adventurous, there's Bock and Oktoberfest.
Porters are like the weird cousin of ales and lagers. They are fermented in a dungeon, with a strong, dark flavor. They're like ales, but with more mystery.
Want to learn more about Robust Porters or English Porters?
These are the styles you should probably not try at home. They're for the experts, and the brave. They're like ales, lagers, and porters, but on steroids.
Or, if you're feeling particularly bold, check out Imperial Pilsner and Wild IPA.