A compound is best described as a substance with two or more chemical elements bonded together. Carbon dioxide, for example, is a compound of the elements carbon and oxygen.
It's worth noting that a chemical compound can have different ratios of different elements in its structure. Water, for example, has two atoms of hydrogen and one atom of oxygen in a ratio of 2:1. All three of these atoms are connected by chemical bonds, which can take the form of covalent bonds, ionic bonds or electrostatic interactions. The nature of the bonds and the elements determines the shape of a compound.