Unfortunately, Airbnb do not offer insurance – they have what is called a guarantee which in the UK is worth £600,000 but they expressly state on their website that it is not an insurance policy, and they highly recommend taking out insurance that would cover guests staying. The grey area occurs when damage may or may not have been caused by guests, thus often normal home insurance will not pay out as guests may have been involved, and nor will Airbnb as they may not. Guardhog covers that gap, so you are fully ensured either way.
Extract taken from Airbnb website: "Airbnb offers you our Host Guarantee and Host Protection Insurance, but please note this does not take the place of homeowners or renters insurance or of adequate liability coverage"
Home Insurance remains the homeowners responsibility, so please do make sure that you have the right cover in place to cover your home sharing activities.