We come across homogeneous and heterogeneous products in our everyday lives. Basically we subdivide a mixture into homogeneous and heterogeneous mixtures. In simple words, in a homogeneous mixture, you cannot differentiate the its components easily. Components in a heterogeneous mixture can be easily differentiated. An example of a homogeneous solution can be a salt solution. We cannot see the different components of the solutions separately as water and salt. An example of heterogeneous solution is a mix of water and petrol. In this, the different components are separately visible.
In a homogeneous mixture, the appearance is uniform and so is the composition. Most homogeneous mixtures are solutions. In solutions, if one of the components is a powder or a liquid that dissolves with the other liquid, then we will not be able to see the different components separately. We see it as one liquid. Air without any visible particles also is a homogeneous mixture. But in fact air is made up of various gases.
In a heterogeneous product, we can easily distinguish the different components in it. If you try to mix sand and water, it will not dissolve. So you can easily distinguish between the sand and the water.
We also have homogeneous and heterogeneous catalysts. A homogeneous catalyst is used in the same phase as the reactants and will be in the same state of matter as the other reactants. Heterogeneous catalysts are used in a different phase from the reactants and it can be in a different matter of state from the reactants.
The components of heterogeneous mixtures can be separated very easily but separating the components of a homogeneous mixture can be difficult. If you have a heterogeneous mixture of sand and water, you can just allow the sand to sediment and separate the components. If you have a homogeneous mixture like a sugar solution, you will have to separate it by the process of evaporation. Other methods of physically separating the components of a mixture are filtration, using a magnet, crystallization, distillation, decantation, and sieving. If you have mixture of sand and iron fillings, use a magnet to separate it. Spread out the mixture on a surface and move the magnet over it. The iron fillings start clinging to the magnet.
You can say that an atom is heterogeneous as it is comprised of protons, neutrons, and electrons. But a molecule can be homogeneous as it is comprised of atoms.