Chocolate milk is a colloid.
Mixtures are divided into two large categories - heterogenous and homogenous. Homogenous mixtures are uniform throughout (homo = the same). All solutions are homogenous mixtures. A homogenous solution has equal solutes (things that are dissolved) throughout all areas of the solvent (the thing that does the dissolving). Heterogeneous mixtures are not uniform throughout (hetero = different). Examples of heterogeneous mixtures are salads and trail mix. Every bite eaten or handful grabbed will have a slightly different ratio of ingredients.
Other examples of homogeneous mixtures are colloids and suspensions. The difference between colloids, suspensions, and solutes is based on the particle size of their solutes. Solutions have the smallest particle size. Colloids are homogenous mixtures with intermediate particle size. And suspensions have the largest particle sizes.