There is nothing like reading the entire DOCSIS 2.0 specification!
The main pieces of the puzzle (at least for DOCSIS only) are:
CMTS = Cable Modem Termination System (where all the CM's eventually connect to) - complete with line cards, a supervisor module and a link "somewhere else" (e.g. the internet)
Provisioning System = Some system at the headend that runs at the very least a tftp, dhcp, and some sort of conditional access provisioning software to manage all this. This also includes the DOCSIS binary configuration generator and any related encryption key generators as well.
HFC Network = Hybrid Fiber Coax network that takes in RF signals on coaxial cable from the headend, converts them to optical fiber and then shoots them down to the neighborhood tap where the reverse is done and the lines go to the houses. Same happens for the upstream direction.
Network wise, most MSOs have at least two networks, a private management network and a public Internet network. Each CM gets at least 2 addresses (PacketCable Devices and CableHome devices typically get 3). SNMP is used alot to do things.
Depending on the age of the equipment, you may see:
Upconverters - Nothing more than devices that take in an input at a certain RF frequency and kick it up into the actual DOCSIS spec frequencies (nowadays most line cards on CMTSs do this automatically). Old line cards did not do upconversion and only output at a base frequency.
Edge QAMs - For newer DOCSIS 3.0 implementations (or the seperate M-CMTS standard), some vendors like Cisco use edge QAMS which take in an optical fiber datastream and do the appropriate QAM modulation and send it down the line. This lets MSO's reuse edge qam's which they tend to have tons of anyway and thus simplifies the CMTS from having this equipment (AKA M-CMTS I believe).
In any case, I used to be a DOCSIS engineer for Cisco, if you have any specific questions on the network, just let me know. I had experience with the Cisco ubr7200vxr and the UBR10K, but most of the knowledge is fading......