This introduction to INLA and the INLA package covers the basics as well as some advanced features. The aim is to provide the reader with a general overview that will be useful to follow the other chapters in the book on spatial models with the SPDE methodology. Other recent works that describe INLA are the following: Blangiardo and Cameletti (2015) provide an introduction to the main INLA theory and an extensive description of many spatial and spatiotemporal models. Wang et al. (2018) provide a detailed description of INLA with a focus on general regression models. Similarly, Gómez-Rubio (2019) describes the underlying INLA methodology and describes many different models and computational aspects.