You need to know their structure, how they clean things (analysis in terms of intermolecular forces, micelles, hydrophobic, hydrophillic etc.), advantages and disadvantages of each (such as why would you use a detergent over a soap which is because of hard-water or environmental impacts of soap vs detergent) and general equation of how the soap is made.
There's no need to memorise like the full soaponification method, because it is not a dot-point in the syllabus. Having some general understanding of it is good, but whenever they want you know about the practical they will have put it as a specific dot point. For example, for esters they stated you needed to know production so that's why the procedure is important in that one