The best thing we can do with knowledge is to share it, the advances in society prove it, and this is the raison d'être of this book. To make available to anyone who may be interested in the teaching-learning of mathematics, our own experiences and some of the knowledge that has been recorded throughout our own teaching practice at the secondary and high school levels, and most of the time at university. Thus, with this book we want to put our own grain of sand in the immense sea of educational work in mathematics. We hope that through the ideas, proposals and theories presented here, the reader will be able to incorporate into his or her teaching practice - and why not, learning practice as well - elements that will allow him or her to enrich, include, build, design and even create new experiences in the classroom.