Mixtures in chemistry are combinations of different substances where each substance retains its chemical properties. Generally, mixtures can be separated by non-chemical means such as filtration, heating, or centrifugation. A solution is a homogeneous mixture, but that's not the full definition. Homogeneous means that the mixture is the same all the way through. Homogeneous mixtures do not settle out if left to sit undisturbed, whereas a heterogeneous mixture would.
Blood is a good example of a heterogeneous mixture.
A solution is a homogeneous mixture where all particles exist as individual molecules or ions. This is the definition of a solution. By the way, there are homogeneous mixtures where the particle size is much larger than individual molecules. However, the particle size is so small that the mixture never settles out. Terms such as colloid, sol, and gel are used to identify these mixtures.