Beer is a type of alcoholic drink. It is made with water, hops, barley (types of cereal grains), and types of yeast (a fungus that produces alcohol). A process called fermentation turns sugar into alcohol, using yeast. Another product of the fermentation is carbon dioxide.
In general, all alcoholic drinks where yeast turns sugar into alcohol are called beer. In these cases, distillation is not used. The difference to wine is that with wine, sugars from plants, such as fruit sugar, or that made by animals is used. As an example, mead is a wine made from honey. Japanese sake is made from rice, and uses yeast for fermentation; so even if some people call it rice wine, sake is really a kind of beer.