Tell me all about beer

Dark beers are usually classified as Stouts or Porters
Ales and Lagers are usually IPA's and various endless other kinds.

Ales are top fermentation yeasts, which means the yeast sits at the top and allows much darker of a beer to be created and allows a much deeper flavor.

Lagers are bottom fermentation yeasts wherein the yeast settles to the bottle and has much more subtle and lighter flavors.

Stouts are 9/10 classified as Ales and have 5 or so major categories: Irish Dry, Sweet, Oatmeal, Foreign, and Imperials. Imperials tend to be the darkest of the bunch but different vendors make them differently.

But as a good guide I'll paste this:

This goes from Lightest to Darkest
Pale lager, Witbier, Pilsener, Berliner Weisse - these will be lighter and almost equivalent to a coor's light
Maibock, Blonde Ale
Weissbier
American Pale Ale, India Pale Ale - this is usually hoppier than normal and has a slightly darker / golden color to it
English Bitter, ESB (my personal favorite, it's very caramel like in color and has a wide variety of flavors, if I had to say it was similar to anything else i would say a mix between a yuengling and an ipa)
Biere de Garde, Double IPA (slightly darker and deeper than a yuengling or esb)
Dark lager, Vienna lager, Marzen, Amber Ale
Brown Ale, Bock, Dunkel, Dunkelweizen (the most widely found brown ale I can vouch for is Newcastle Brown - almost light a hazelnut caramel color)

Here is where the darker beers come along:
Irish Dry Stout, Doppelbock, Porter
Stout
Foreign Stout, Baltic Porter
Imperial Stout

Most of the time stouts and porters taste slightly more chocolatey (cocoa ish) than other beers but are more often packed with antioxidants and flavor. Also, most of the time the darker the beer the less carbonated they are. Which is why Guinness has the carbonation ball thing in it to keep the beer tasting fresh. This also explains why these darker beers taste much better at room temperature or slightly warmer than a normal beer - because you can taste the subtle flavors much more and the carbonation won't be affected.

Also By Country:
BELGIUM
Abbey Beers:
Belgian Browns:
Golden/Blonde:
Lambics:
Red Beers:
Saisons:
Trappist Beers:
White (Wit) Bier:
GERMANY
Alt Bier:
Beliner Weisse:
Dunkel-weizens:
Hefe-weizen:
Bocks:
ENGLAND
Barley Wine:
Bitters English:
Ordinary bitter:
Special bitter:
ESB (Extra Special Bitter):
English Browns:
India Pale Ale (IPA):
Pale Ales:
Porters:
Oatmeal Stouts:
Sweet Stouts (or Cream Stouts):
Strong Ales:
SCOTLAND
Scotch Ale:
Scottish Ales:
Scottish Light Ales:
Scottish Heavy Ales:
Scottish Export Ales:
IRELAND
Dry stouts:
FRANCE
Bier de Garde:
VARYING COUNTRIES
Foreign-style Stout:
Imperial Stouts:
Winter Warmers:

http://s3.amazonaws.com/theoatmeal-img/comics/beer/6.png

sorta irrelevant, but fun.

Dark beers are usually classified as Stouts or Porters
Ales and Lagers are usually IPA's and various endless other kinds.

Ales are top fermentation yeasts, which means the yeast sits at the top and allows much darker of a beer to be created and allows a much deeper flavor.

Lagers are bottom fermentation yeasts wherein the yeast settles to the bottle and has much more subtle and lighter flavors.

Stouts are 9/10 classified as Ales and have 5 or so major categories: Irish Dry, Sweet, Oatmeal, Foreign, and Imperials. Imperials tend to be the darkest of the bunch but different vendors make them differently.

Um, no.

The strain of yeast used has no affect on the final color of the beer. Color comes from the Lovibond of the grains used, and their ratios. Dark grains also tend to impart some flavor to the beer - like roasty or chocolatey - but that's not guaranteed either. Carafa III has little of the roasty bitterness, but adds a deep black colour. It is often used for Black IPAs where you want the color but not the flavor.

The more subtle light flavor of a lager comes in part from the yeast (lager yeasts tend to be "neutral") but primarily from the grist, which will have a high % of (usually) pilsner malt, which has a low lovibond rating. Also, lagers tend to be more subtly hopped. Again though, not guaranteed: Black American Lagers are not light, and a Munich Helles can be quite roasty and complex.

Some ale yeasts - e.g. typical English ale yeasts, like Ringwood - can be quite fruity (produce esters); but some - e.g. American yeast 1056 - are "cleaner", letting the hops come through more.

Most of the time stouts and porters taste slightly more chocolatey (cocoa ish) than other beers but are more often packed with antioxidants and flavor. Also, most of the time the darker the beer the less carbonated they are. Which is why Guinness has the carbonation ball thing in it to keep the beer tasting fresh. This also explains why these darker beers taste much better at room temperature or slightly warmer than a normal beer - because you can taste the subtle flavors much more and the carbonation won't be affected.

Again, not strictly correct...

The widget in a can of Guinness is actually nitrogen, not carbon dioxide. English beers are served with low carbonation as that is the style, not because of the color. But yes, serving warmer (55 F) is better to allow the aromas (esters, hops, grain) to better develop. Light American Lagers taste crap at this temp (or any temp for that matter) because they have no hops, aroma (other than some "corn" from DMS) or flavor to speak of.