The Science of Shampoo
There are some things hair products can do, and some things they can’t do. The most important point to understand is that hair is not living tissue. It has no circulatory system and cannot metabolize anything. Some products claim to deliver vitamins or other nutrients to your hair. This is not possible.
Hair does reflect what we eat and what we have in our system, so if you want to get vitamins and nutrients into your hair, you have to eat them and wait for new hair to grow.
Existing hair cannot metabolize or otherwise absorb nutrients or vitamins; its makeup comes from your circulatory system, not from anything you put on it topically.
But compounds can be applied to the surface of hair. Think of polishing a table or waxing a car. This is what conditioners do to your hair; they add a layer of some coating. Hair strands can split or fray or become otherwise damaged; silicone polymers from conditioner can fill in those gaps and sort of glue it back together, making it appear smooth or shiny.
In short, the active ingredients in shampoos are detergents for washing stuff off; and the active ingredients in conditioners are polymers that add a coating back on. They basically do what they say, so long as they don’t say they do anything more than that.