Homogenous means "of the same kind or nature." It is used to describe something that is uniform or consistent in composition. For example, a group of people who are all the same age or a liquid that is the same color throughout would be considered homogenous.
Homogeneous means "having the same physical properties throughout." It is used to describe something that has the same density, temperature, pressure, etc. throughout. For example, a piece of metal that is the same temperature all the way through or a gas that has the same density everywhere would be considered homogeneous.
In general, homogenous is used to describe things that are made up of the same material, while homogeneous is used to describe things that have the same physical properties.