Ammonium Lauryl Sulphate (ALS) and Sodium Lauryl Sulphate (SLS) are different substances but they do a similar thing in formulations. They are both called surfactants. They break surface tension of water and help the cleaning of the hair and scalp.
SLS has a much smaller particle size and there is a worry it can penetrate the skin. It is also more aggressive in its cleansing action. ALS is much bigger particle size and is much kinder and less reactive with the skin.
But in order to clean the hands or hair even the mildest soap has to help break down dirt and grime. This is what ALS does. We pick a naturally derived ALS which comes from coconuts.
But ALS while much milder still does an effective job at helping to remove grime and dirt from the hair and scalp.