Main ingredients

The main ingredients in beer include water, yeast, malt, hops, and what ever else we, or beer companies think of.

For the water, never use tap or distilled water. This would potentially ruin what you believe your beer is going to turn out to be. Seeing as though water is the main ingredient in beer, I would just stick with using filtered water.

Yeast, its what makes beer...beer. It creates the alcohol and the carbonation of the beer. Without yeast, you'd just have a brown liquid that looks like murky water. *gag*

Malt, it's what makes beer sweet. Without malt, beer would be a carbonated, nasty tasting coffee/tea liquid.

Hops, this enhances the beer. It's kind of like a condiment. Like seasoning on a cut of meat, it enhances flavor and overall aroma of the beer. It's what seperates good, high quality beers, from low quality cheap beers.

Other ingredients can include berries, and many other types of fruit. Whatever you can think of that will give the beer its kick.