Milk is an emulsion. An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable), such as oil and water. In milk, the fat globules are dispersed in the water phase. The fat globules are stabilized by a layer of proteins, which prevents them fromcoalescing (coming together).
A suspension is a heterogeneous mixture in which the particles of one substance are dispersed throughout another substance. The particles in a suspension are larger than the particles in an emulsion, and they will eventually settle out of the mixture.
A foam is a dispersion of gas bubbles in a liquid or solid. The gas bubbles are stabilized by a surface-active agent, such as soap or detergent.
A gel is a solid that contains a significant amount of liquid. The liquid is held in place by a network of solid particles.
In conclusion, milk is an emulsion.