Biscuits vs. Cookies

It's a more complicated question than you'd imagine, and it can be confusing.

In American English, biscuits are leavened and may be savory or slightly sweet. The term 'leavened' means that baking soda or yeast is used. Think of KFC biscuits.

However, those biscuits look and feel very much like scones. So in British English, they would be scones, not biscuits. In Britain, all kinds of round, flat, and sweet baked goods are called biscuits. Think of digestive biscuits. They are originally from Scotland, in Britain. The term 'cookie' is not very often used in Britain.

In North America, on the other hand, nearly all of the sweet, rounded and flat baked goods are called cookies. Think of chocolate chip cookies.

To sum up:
American biscuits=British scones
British biscuits=American cookies
In America, the word 'cookie' is very generally applied.
In Britain, the word 'biscuit' is used more often.

You'll have to judge case by case, but these are the general rules.

Bread is leavened and plain (and maybe a little savory), although it can have sweet ingredients(raisins or chestnuts, for example). It's still basically savory, though only slightly so, in most cases.