Beer gets its flavor primarily from two ingredients: malt and hops. The malt gives the smooth and sweet flavors and hops provides the biterness. For the beer newbie, malt is made from barley by spraying it with water, allowing it to germinate, and then drying it in an oven. The various flavors of malt are made by heating the malt further after it is dried. The hotter it gets the darker and generally sweeter. Some common colors of malt are carmel malt, chocolate malt and black patent malt. The black malt is less sweet because a lot of the sugar is burnt.
An individual beer recipe is a balance between how much malt is added, what color malt is added, and how bitter to make it with hops. Something like Bud has little malt and not too much hops. Rice or corn is added to increase the alcohol content without increasing the maltiness. To my taste, a nice pale ale made with all malt and no other grains is much better, being maltier and a bit sweeter.
Increase the malt content significantly and you have something like a scottish or scotch ale. These have a higher alcohol content and are very malty and fairly sweet. As they get sweeter, the brewer tends to offset by adding more hops to maintain the balance of sweet and bitter, but these types of ales are still left on the sweet side.
Go from here and increase the hops a lot, and you have IPA, India Pale Ale. It was formulated with high alcohol and hops to preserve the beer from spoiling as it was transported from England, around the continent of Africa, to India. People who like hops like IPAs.
Go down a notch in malt and back way off the hops, and then add some chocolate malt and a little black patent malt and you have porter. Porters vary a lot in how much black malt they have (how much they taste roasted or burnt). The sweet ones are almost like a desert, while the more roasty are less so.
Add a whole lot more black malt and you have a stout, somewhat like a beer coffee.
And then of course, there are a gazillion other styles...
Hope this helps without being too wordy.