SOAR, located on Cerro Pachón in Chile, is a recently completed 4.1 m telescope, dedicated to high angular resolution. To complement the other two larger telescopes, Gemini on Cerro Pachón and the Blanco telescope on Cerro Tololo, SOAR's niche is high resolution, imaging in the visible and spectroscopy, which calls for the development of an adaptive optics (AO) module. This instrument will provide improved seeing over a wide field, for visible wavelengths. In this paper, I briefly describe which kind of science can be carried out with this type of AO and compare its performance with other ground-based and space-based telescopes. Then, the ground layer compensation principle and its application for Pachón atmospheric conditions are presented. Most of the nights, the perturbations are located close to the ground; thus a partial correction of the first kilometer of the atmosphere will be efficient to improve the seeing significantly (by a factor of 2 or more). Finally, technical details on the instrument itself including the deformable mirror, the wavefront sensor, the laser and the turbulence simulator are given.