The word "pagaré" in Spanish means literally "I will pay".
To understand a pagaré it is important to know that Spanish cheques are payable upon presentation - regardless of whether they are post-dated or not. A Pagarés then, is a type of cheque that emphasises the date that it can be cashed. These then, are official post-dated cheques.
Pagaré come in a chequebook, just like normal cheques.