At a macroscopic level (or a bulk level), all matter can be classified as pure substances and mixtures. Matter classified into each of these categories can be further sub-categorized into the following subcategories:
A mixture can be classified as a homogeneous mixture or as a heterogeneous mixture. In a homogeneous mixture, the particles of the different constituents mix completely with each other. A solution of table sugar in water is an example of a homogenous mixture. In a heterogeneous mixture, the components do not mix together in a uniform way. The composition of these mixtures can vary at different points. An example of such a mixture is a mixture of sand and sugar.
A pure substance can be classified as an element or as a compound. Elements feature only one specific type of atom. Molecules, on the other hand, feature the presence of more than one elements (in a fixed ratio).