A third party insurance is an insurance policy that protects against claims from a 3rd party. The insurance broker is considered the 2nd party in this contract. It's often called a liability insurance since it's insuring for risks of liabilities coming from lawsuits and other legal problems. There are several different types of third party insurances: third party car insurance, third party insurance for dogs.
Third party car insurance
A basic third party insurance for your car is a legal obligation in the UK. The minimum is a TPO (third party only) car insurance, although most drivers opt for a TPFT cover for Third Party damage, Fire and Theft. TPFT policies provide a much better level of protection, although not as much as a comprehensive car insurance would cover.
TPO car insurance
A basic TPO car insurance covers damage done to another vehicle in case of crash even if it's your fault. It also covers possible legal costs. It does specifically not cover damage to your own car or fines. In fact, fines are never covered by any legally available insurances. Any kind of insurance in the UK will have this basic cover, this includes a car insurance for one day, one month and 6 months.
TPFT car insurance
A TPFT third party car insurance will also cover any damage done because of theft or fire. This includes your car stereo.
TPFT or TPO insurance also does not cover you for medical expenses. However, if the damage was caused by another driver your medical expenses are going to be covered by the faulty driver's insurance. And of course you have health insurance that will cover the blunt of the expenses.