A mixture is two or more chemical substances which have distinct properties that can be separated, usually through physical means due to the different properties that each substance has.
A container filled with sand and iron dust can be separated by a magnet for example.
For example air is a mixture of various gases. Metal alloys are also mixtures.
There are various kinds of mixtures that often depend on the phases of the two substances.
A colloid is a substance microscopically dispersed throughout another substance
An emulsion is a mixture of two or more liquids that are normally immiscible (nonmixable or unblendable). Emulsions are part of a more general class of two-phase systems of matter called colloids.
Mixtures of oil and water are also examples of substances that can be separated.