AFM is Atomic Force Microscopy, or the Atomic Force Microscope. AFM was developed after initial work on STM - Scanning Tunneling Microscopy. Later, AFM spawned its own variations, such as Magnetic Force Microscopy (MFM), Lateral Force Microscopy (LFM), Scanning Nearfield Optical Microscopy(SNOM), etc, etc.
There are LOTS of such techniques that usually use the same method as the AFM of scanning a probe close to the sample surface, these often differ in the properties they measure.
Together, these related techniques together are referred to as Scanning Probe Microscopy (SPM). Another term sometimes used is Scanning Force Microscopy (SFM), which is a synonym for AFM.