Frankly speaking, cabling systems are a complicated thing. With so many wires involved, a group installing them should be knowledgable in every aspect from wirings to design and structures. There are many types of cabling systems, as they are categorized in terms of the data rates that they can sustain effectively.
The specifications describe the cable material as well as the types of connectors and junction blocks to be used in order to conform to a category. For ISO/IEC standards, the category refers to the cable and class refers to the connector. ISO are international standards and can be followed anywhere in the world. A standard is different than a code in that standards are voluntary and provide a guideline so that all manufacturers have a minimum set of parameters to work with. A code, on the other hand, is law and is enforced through an AHJ (Authority having Jurisdiction).
While longer connections for Gigabit Ethernet use fiber optic cables, the goal is to leverage the CAT 5 and CAT 5E twisted-pair wiring most organizations already have in place for connections out to the desktop. (Four pairs of twisted pair are used.) In old split pair configurations, PoE MidSpan can not be used. PoE is supported on 5e or better; however the higher performing cable provides better heat performance with shielded systems better than UTP.