ASCOM is the general name for enabling technology based on universal connectivity between astronomy apps/programs and the devices they use. ASCOM has thus opened up astronomy software innovation by eliminating the need to write special code for each device. ASCOM itself represents the definitions or patterns which are called Interfaces. These establish the universal language used between apps and devices.
ASCOM COM is the classic ASCOM which uses the COM service on Windows to provide communication between apps and devices. ASCOM Alpaca is the newer ASCOM which uses network communication between apps and devices. Alpaca works on Linux, MacOS, Windows, and even on embedded controllers. ASCOM COM is limited to Windows.
Take a few moments to reflect on this little flip chart presentation and imagine the possibilities. Then for more in-depth historical and technical detail, look through the info indexed in the orange menu on the upper-left.
Now that you understand the possibilities offered by ASCOM universal connectivity, you can get a bit deeper with some info on modular architectures, of which an ASCOM-bades observatory is an example. Onward to 2. Modular Architectures.