From NSDL Materials Digital Library Wiki
A Cell List is a technique for speeding up the evaluation of short-range interactions in a system of particles. Given that (1) each particle has a cutoff radius rc beyond which it does not interact with other particles, (2) the cutoff distance is smaller than the the simulation box, then it is calculationally advantageous to exclude from energy and force calculations particle pairs that are not interacting.
If the simulation space is divided into cells of size then a particle in any given cell is guaranteed to interact only with particles in its cell and the 26 neighboring cells.
By combining this method with Neighbor List method, that is, by using cell lists to construct neighbor lists when neighbor lists are triggered to be reconstructed, an even more efficient calculation can be implemented.