The ESASky module in Astroquery is basically the python interface for ESASky. You can read more about exactly what ESASky is here, but to summarize ESASky is a website that gives users a single, easy-to-use interface for accessing petabytes of data from all ESA telescopes and a few JAXA and NASA telescopes.
The ESASky module fuses the power of ESASky with the thriving python community in astronomy. This community has among other things developed the Astroquery package, which is an open source project, currently is maintained by Adam Ginsburg. This project is an affiliated package of the larger Astropy project, which tries to solve the needs among the growing python community in the astronomy scene. The Astropy project contains loads of different tools for scientists to use, while Astroquery focuses on fetching data from telescopes both on earth and in space.
The ESASky module allows users to download both calculated metadata for the different mission catalogs and the FITS files, which are filled with both images and science data. This allows users to access petabytes of data from the world’s space telescopes and analyze it with their favorite python tool.
Currently, I am the sole developer and maintainer of this module.