A warranty is a guarantee or assurance.
Section 2 of the Sale of Goods Act 1908 provides that:
"Warranty" means an agreement with reference to goods which are the subject of a contract for sale, but collateral to the main purpose of such contract, the breach of which gives rise to a claim for damages, but to a right to reject the goods and treat the contract as repudiated.
With respect to goods, a warranty is the manufacturer's or trader's guarantee that goods or services will last as long as the warranty says it will. The terms and conditions of the warranty are decided by the manufacturer or trader and might cover more or less than the Consumer Guarantees Act 1993 offers. The warranty doesn't replace your rights under the Consumer Guarantees Act 1993.
When selling your home, as vendor you will usually be required to give certain warranties and undertakings. Before signing any Agreement for Sale and Purchase, have Rennie Cox explain the document to you, and the implications of each item which you are warranting. Never sign any significant contract, including an Agreement for Sale and Purchase, without legal advice.