J-PAS is a planned large photometric survey which will scan ~8000 deg^2 of the northern sky with 56 contiguous narrow-band filters that cover the entire optical range. The survey will be conducted from a dedicated 2.5m telescope recently built at the Observatorio Astrofisico de Javalambre, and equipped with a 4.7 deg^2, 1.2 Gpixel camera. Given its unique filter configuration and large field of view, the survey will effectively and efficiently provide a low-resolution spectra for every observed pixel, allowing an unprecedented precision in object classification and photometric-redshift estimation. The wealth of data that the survey will deliver are expected to provide significant contributions in many areas of astrophysics. In this talk I will give a broad overview of the survey, from its technical description to its expected scientific impact, focusing in particular on cosmological experiments and galaxy evolution studies.