how is shampoo an emulsifying agent? How does it work?

emulsifying agents are what are called amphipaths ..that is they have one end that is non-polar ( so it can interact with greases, dirt, waxes , etc that are not easily water solublke ) and a polar end that will interact with the water phase. This allows the two immiscible entities non-polar and polar to be brought together in a phase transfer arrangement.( Like what soap-suds do with kerosene and water ). This helps to break apart grease and fat and wax globules and solubilize them.   Alkyl sulfonates , and monoglycerides are commonly used in shampoos because they are readily available  and useful amphipaths.