When light waves are incident on a medium for example on gas, the waves encounter molecules and atoms of the gas. The light wave deviates from its path and gets scattered in all possible directions. The light wave is absorbed by the molecules and radiated back in all directions. This is called scattering of light radiation. These molecules are called the scattering centers.
In a solid or liquid too, the molecules or particles that radiate the incoming radiation energy in
all directions are called scattering centers.
Almost all gas molecules are scattering centers.
When there is laser beam (highly directed) between two points far from you and across us, we are able to view this beam because of scattering of laser light into our eyes.
see diagram too.