AM/FM/GIS stands for Automated Mapping/Facilities Management and is a subset of GIS, which is associated with public utilities like gas, electric, water and telecommunications. The term AM/FM/GIS mostly refers to GIS software that allows utility users to digitize, manage and analyze their utility network data. This data is stored in an underlying GIS database which also maintains the associations between the graphical entities and the attributes.
Read more about AM/FM/GIS: Components, Architecture, Advantages