Full definition
Public liability insurance is defined as: Public liability insurance covers a business against claims for injury or property damage caused to third parties in the course of its work.
Public liability is the baseline cover most clients demand from any supplier that comes on site or interacts with the public. Standard UK limits range from £1m to £10m depending on the client and the work.
Evidence is usually a certificate of insurance naming the insured entity and the limit. Verify the limit meets your contract minimum and that the policy is in date on the day work begins.