Compound

is a physical condition.

Compounds are a type of item used in chemistry, which are created from combinations of various elements.

Obtaining
Compounds cannot be obtained in the creative inventory. They are only obtained by creating them in the compound creator. This is done by inserting a certain number of elements corresponding to the compound's chemical formula. Unlike most GUI blocks, the elements are not consumed.

Natural compounds
Natural compounds are compounds which can be obtained naturally in Minecraft.

Garbage
Garbage is considered a "compound", but the only way to produce it is to activate the Lab Table when its inputs aren't a valid recipe. It has no uses.

Usage
Certain compounds are used as ingredients in crafting or lab table experiments. Natural compounds have uses outside of chemistry, detailed in their respective articles.