HongaarseBeer

I'd wager that it works in much the same way as soap. ie. it is made from fatty acids with hydrophilic and lipophilic sides. The lipophilic side binds to sebum produced by the body, and the hydrophilic side binds sweat. And then when you rinse with water, the hydrophilic side binds to the water and gets rinsed away. 

There are probably some other components in soap specifically to remove dandruff, and various agents to provide a pleasant smell and texture to the shampoo... Probably, I haven't actually read anything about shampoo. 

Thank you very much. I didn't expect such a well-defined answer