Suspensions are in which the particles that are floating around are big enough to sink to the bottom - mud is an example. If you shine a light through it after this has happened, you won't see anything because there are no particles to see.
are mixtures in which the particles have actually dissolved. As a result, there are no particles to see when you shine a light on it. Salt water is an example.
Colloids, on the other hand, have small particles that float around and never settle. If you shine a light on them, you'll see the scattering characteristic of the Tyndall effect. Incidentally, colloids usually appear cloudy when a light is shined on them, unless there's not very much stuff floating around.