What is dirt?

To understand how any cleaning product works we must understand what dirt is or rather what it is comprised of.
Dirt is a actually layer of fine films made up of fats, oils, and grease (FOG), bacteria, fungi, dust mites, non-organic material and other organic micro-organisms. These films are bonded to each other and to the surface by amino and fatty acids.
FOG is a combination of plant and animal fats known as lipids as well as mineral oil products which are all organic in origin. The method used in most cleaning solutions is to emulsify FOG, which is to put it into an emulsion or solution such that it can be relocated elsewhere through rinsing.

Dirt has layers of fine film composed of “substrate” such as grease, oils, fats, bacteria, germs, dust mites, non-organic material and organic microorganisms. These films are bonded to each other and to the surface by amino and fatty acids (organic acids composed of proteins, fats or fatty oils). 
Most cleaners emulsify some of these dirt films but may not break down the lower levels held together by amino and fatty acids. 
Usually the top layers of the films are removed but some of the lower levels are left to collect bacteria. As a result, re-soiling can occur much faster.

The primary function of cleaning is to reduce dirt, dust, bacteria and moulds from surfaces.

Cleaning agents generally separate soils from fabric or surface substrate by dissolving or suspending them in a water or solvent liquid solution to be carried away when the solution is removed. 
The cleaning action of the primary formulation components is supplemented by additives to optimize the performance of the cleaners.

Bio clean products replace synthetic chemicals with bacteria and or enzymes to effectively remove dirt from surfaces.