The difference between public liability and products liability insurance is quite distinct, despite products liability and public liability being offered as a combined policy (as with Qdos policies) or sometimes as an add-on. Products liability doesn't tend to be offered as a standalone product.
Both public liability insurance and products liability insurance policies cover third party claims for injury or damage to property, however each insurance will react in different circ*mstances.
Public liability insurance reacts in circ*mstances in relation to the delivery of your services, whilst Products liability reacts in circ*mstances in relation to products you have manufactured, supplied, or sold.
For example, if you were to cause injury to, or damage the property of a third party in the delivery of your services such as accidentally leaving a wire on the floor which causes someone to trip and fall, and that person took legal action against you, this could give rise to a public liability claim.
If you sold a client a product which subsequently caused a third party bodily injury or damage to their property, whether from a manufacturing defect, design defect or failure to provide adequate warnings, and the third party took legal action against you, this could give rise to a products liability claim.