MMA welding refers to a welding method where a filler electrode in the electrode holder serves as the welding electrode. The arc burns between the electrode and the work piece.
The difference to other welding methods is that the welding electrode in MMA welding shortens continuously as the welding progresses. In TIG and MIG/MAG welding the distance of the torch from the work piece must remain constant at all times. In MMA welding, however, the electrode holder must continuously be brought toward the work piece to keep the distance between the electrode and the molten weld constant.