IEEE 802.3 is a working group within the Institute of Electrical and Electronics Engineers (IEEE) professional organization. It is also a collection of IEEE standards produced by the working group defining the physical layer and the media access control layer (MAC) of wired Ethernet (There are other groups responsible for wireless, etc). These standards define technology, generally specific to local area networks, with some wide area network applications. The standards define the physical connections between nodes and/or infrastructure devices like hubs, switches, routers, etc. and various types of copper or fiber cable.
The Telecommunications Industry Association (TIA) defines the performance for structured cabling at the component level, link level and channel level to support an application over the distance specified. Sometimes a new category of performance must be defined to support a new application. The purpose of standards is to provide the minimum requirements to guarantee applications will function properly with equipment from any manufacturer. Using TIA structured cabling assures interoperability between components from different manufacturers.