Scanning probe microscopy is the umbrella term for all kinds of microscopy techniques, where the sample is not imaged at once, but scanned line by line.
The best established modes are:

• STM: scanning tunneling microscope
• AFM: atomic force microscope
• SEM: scanning electron microscope
• confocal laser scanning microscope
• NSOM : near-field scanning optical microscope

The main advantage of the scanning technique is, that the resoution of the microscopes is not limited by diffraction. On the other side, scanning technics are a lot slower in acquiring images, due to the scanning process.