The Prêt à Voter system, introduced by David Chaum, Peter Ryan and Steve Schneider, has been designed to provide secure and auditable elections using cryptographic techniques. Voters can maintain secrecy of their vote, but each voter is provided with a receipt so that they are able to verify that their vote has been properly entered into the system. The receipt is encrypted so it means nothing to others. Furthermore, the system is completely transparent and auditable which means auditors can check in a public way that the result corresponds to the voters cast, providing safeguards against electoral fraud. This paper will give an overview of the Prêt à Voter system at the architectural and system design level. In order to make the introduction more clear, we have divided the Prêt à Voter system into the following three phases: ballot construction phase, ballot casting phase and ballot tallying phase, and we will introduce each of them in turn.