Express warranties are those that are defined specifically in the contract.
Implied warranties are based in statutory and/or common law, depending upon your jurisdiction.
They are two-fold: a warranty of merchantability, which requires that goods/services must reasonably conform to an ordinary buyer’s standards, and a warranty of fitness for a particular purpose, which states that if a seller knows the intended purpose for the product or service, the act of selling the product to that customer implies that it is fit for that purpose.
Be aware of warranty disclaimers and understand how the disclaimer limits your statutory rights. If it disclaims all warranties, express and implied, then you will likely be limited to the remedies in the contract for issues related to things like performance. You should also examine any disclaimer in the context of the contract. While it may require you to disclaim your statutory rights, other contract language may give you adequate rights and remedies regarding the points about which you are most concerned.