A structured cabling system (SCS) is a set of cabling and connectivity products that integrates the voice, data, video, and various management systems of a building (such as safety alarms, security access, energy systems, etc.).

In other words is the systematic ways or standards for network cabling and telecommunication room issued by the Telecommunications Industry Association (TIA) and the Electronic Industries Alliance (EIA), and other standards organization.

Typically you can see telecommunication rooms in a building divided into three main parts

1. MDF (Main Distribution Frame) or can also be called MC (Main Cross-connect)
MDF is where all of the backbone cables gather, there should be usually 1 MDF in a building.

It contains routers and core switches . There are also 110 blocks/66 blocks use for UTP cables connectivity for data or voice (phone).  UTp cable can be used to connect computers, telephones, speaker attenuators (controllers), alarms, etc.  UTP cable usually have 4 pairs,but it can contain more than 4 pairs i-e. 25 or more

In MDF, if you use fiber optics for backbone, you should have Fiber Distribution Frame.

From MDF, you connect to a Demarcation Point, used for connectivity to the outside world, this is where the line ends between your responsibility as a network engineer with the service provider.

2. IDF (Intermediate Distribution Frame) or IC (Intermediate Cross-connect)

The IDF is more or less similar to the MDF, but with a smaller scale, only about a couple of meters square room.
This is where the smaller switches located, then you connect the patch cables from the switch to patch panels or 110/66 blocks. Patch panels and 110/66 blocks are equipments where you terminate the cables. Then from the patch panels you connect cables directly to the work area of end users.

3. Work Area
Now this is where the cables end, this is whre the place where end users located. The end users shouldn’t care about how complicate the cables that connect their computers to the network.
The cables from the IDF are spread to the modular jack wall plates, you can use UTP cables or even fiber optics.This is just a scratch on the surface of networking world, it may seems complicated but believe me, if you are in to it, it should not be that hard.