Simple Definition:

An emulsion is a mixture of two or more liquids that do not normally mix together, where one liquid is dispersed (spread out) as tiny droplets in the other liquid. The liquid in which the droplets are dispersed is called the continuous phase, and the liquid that is dispersed is called the dispersed phase. For example, mayonnaise is an emulsion made by dispersing oil droplets in water, and milk is an emulsion made by dispersing fat droplets in water.

Very Simple Definition:

An emulsion is a mixture of two or more liquids that don’t usually mix together. For example, when oil and water are mixed, they create an emulsion.