Here is it in BMW's own words...
Electronic Suspension Adjustment ESA.
The Electronic Suspension Adjustment ESA is a new feature in this motorcycle segment. Available as an option ex works, it allows the rider to conveniently set the rebound stage damping of the rear spring strut at the press of a button on the handlebars, with the settings "Comfort", "Normal" or "Sport" available, thereby adapting the set-up to the needs of both route and riding style. The handwheel for setting the desired spring mount has been optimised for improved controllability.