Geocoding is converting spatial information, such as drawings, maps, photographs and addresses, into digital form for use in geographical information systems (GIS) using scanning, digitizing and address matching operations.
Scanning is the process by which raster data is captured from a paper map. Raster data is a way of representing the earth's surface by subdividing into small pixels.
Digitising is where points or line features are traced either directly from paper maps or from scanned images of the maps to create vector data. Vector data divides space into discrete features, usually points, lines or polygons.
Address matching or geocoding uses the recorded address in conjunction with a digital map or computerised list of addresses to place a street address onto the map in a known location. This usually involves the matching of two files. One file contains the addresses of interest and the other a list of addresses and their coordinates. This process often uses commercial software such as QuickAddress.