The main difference between a heterogeneous mixture and a homogeneous mixture is the degree to which the materials are mixed together. Generally speaking, a heterogeneous mixture is less well integrated than a homogenous mixture.
A heterogeneous mixture is one in which the different components are not especially well mixed. Either the components are not uniform or they have localized regions with different properties. A classic example of a heterogeneous mixture is oil and water. Others include soup or pizza.
A homogeneous mixture is one in which the components are uniformly and smoothly distributed throughout. Examples are air, blood and saturated sugar water.