Use this tag for questions regarding the manual or automatic leveling of the build platform.
Bed leveling is the process of calibrating the level of the bed in relation to other axes (usually the z axis) of the printer. Do note that the term leveling is known as tramming. This is based on the principle of reference (the level of the bed is related to the plane or axis you level it to), and has nothing to do with bubble level.
The process of leveling can be either a manual or an automated process. The latter is frequently used with some sort of a sensor to sense the distance to the platform; such a process is referred to as Auto Bed Leveling (ABL). These sensors scan the build surface to compensate for local or global surface deficiencies.
See also automatic-bed-leveling