2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/145308This is the summary of 4 Lectures given at the XIX Canary islands winter school of Astrophysics ''The Cosmic Microwave Background, from Quantum Fluctuations to the present Universe''. Lectures were intended for master/beginning PhD students in cosmology.To appear in the proceedings of the XIX Canary Island Winter School "The Cosmic Microwave Background: from Quantum fluctuations to the present Universe", comments welcome. (fixed entry of table1)Astrophysicstext