The free / open source nature of the project invite each user to contribute to it. On this page you will find the operationg documentation for the telephone as well as instructions for you to participate on this vast project.
Hardware refers to the whole material part of the phone, from the materials used as the circuits that make it work. The documentation linked below describes in depth all the details.
Software refers to the whole of the phone's software, i.e. the operating system (PaxOS) and the applications running on it. The documentation linked below describes their architecture in detail.