The continuous movement of particles but no overall change in concentration is called diffusion.

Here's why:

* Diffusion is the movement of particles from an area of high concentration to an area of low concentration.

* Even though particles are constantly moving, in a state of equilibrium, the movement of particles in each direction is equal, resulting in no net change in concentration.

So, while the particles are constantly moving and shifting, the overall distribution of particles remains the same. This is a fundamental principle in chemistry and biology, explaining how substances move within cells and throughout the environment.