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Suspensions are a type of mixture where large particles are dispersed in a liquid or gas. These particles are typically greater than 1000 nanometers in diameter. Because of their size, these particles can often be observed with the naked eye or under a simple microscope.
The significant characteristic of suspensions is that they are not stable over time. The large particles tend to settle out under the influence of gravity. For instance, if you imagine a mixture like sand in water, you can see how the sand eventually settles at the bottom.
Another essential feature of suspensions is that they can be separated using filtration. This means when you pour a suspension through filter paper, the filter will trap the larger particles, separating them from the liquid or gas part of the mixture. Suspensions also show the Tyndall effect very clearly, scattering a beam of light as it passes through, due to the large size of the particles.

Colloids are mixtures with particles that range between 1 nanometer and 1000 nanometers. These particles are larger than those found in solutions but smaller than those found in suspensions.
Because of their intermediate size, colloidal particles are not visible to the naked eye but can be seen with the help of a microscope. Despite this, colloidal particles do not settle over time, which makes colloids appear uniform.
Unlike suspensions, colloids cannot be separated by standard filtration methods because the particles are too small to be trapped by filter paper. Colloids do, however, produce a Tyndall effect, scattering light as it goes through them, although this is less intense compared to suspensions. A classic example of a colloid is milk, where the fat droplets are dispersed through the liquid.

Solutions are mixtures where particles are present at the molecular or ionic level, which is usually less than 1 nanometer in size. These mixtures are completely homogeneous, meaning they have a uniform composition throughout.
Since the particles in a solution are so small, they are invisible to the naked eye and even under a microscope. This also means that solutions do not separate over time; the dissolved substances are evenly spread out in the solvent.
Separation by filtration is not possible in solutions, as the particles are too small and are not suspended but dissolved at the molecular level. Solutions do not exhibit the Tyndall effect because there are no large particles present to scatter light. A simple example of a solution is saltwater, where salt (sodium chloride) is dissolved in water.