Homogeneous refers to a substance that is consistent or uniform throughout its volume. A sample taken from any part of a homogeneous substance will have the same characteristics as a sample taken from another area.
Air is considered a homogeneous mixture of gases. Pure salt has a homogeneous composition. In a more general sense, a group of school children all dressed in the same uniform may be considered homogeneous.
In contrast, the term "heterogeneous" refers to a substance that has an irregular composition. A mixture of apples and oranges is heterogeneous. A bucket of rocks contains a heterogeneous mixture of shapes, sizes, and composition. A group of different barnyard animals is heterogeneous. A mixture of oil and water is heterogeneous because the two liquids do not mix evenly. If a sample is taken from one part of the mixture, it may not contain equal amounts of oil and water.