Soy lecithin has been a staple in the food & beverage industry owing to its variable properties. It is core to many food processing functions that determine the quality of the end product.
It's naturally found in soybeans and other plants. The main function it provides is emulsification as it's amphiphilic, enabling it to keep insoluble elements like oil and water from separating.
While it is the most used raw material, it is also, unfortunately, the most controversial due to many of its highlighted adverse effects. Check it this blog and decide for yourself if soy lecithin is harmful or harmless.