At home, I pulled the cable in the wall between the two rooms. Of course, it's about twisted pair. In the walls there are installation boxes for LAN sockets, which I have already bought and I want to mount. I am looking for information on the net how to connect it correctly and I learned that there are two standards A and B. I was able to get information that these standards differ in the connection of wires, but nowhere did I find information what it gives? Why these two standards? Does it affect something what standard is used?
The standards were used to connect specific types of devices that transmitted / received data on specific pins, hence there was a need to swap the transmit and receive pair when combining two of the same types (eg a computer with a computer). Currently, it does not matter what standard you use, as most modern devices use automatic patching. https://pl.wikipedia.org/wiki/Auto_MDI-MDIX
... In times when access to the Internet was still carried out by analogue 56.bps modems, and network equipment like Network Cards from BNC through the hub, Hub Hubs were expensive, and the only alternative was connecting two computers in a network over the LPT port or a much slower COM. , an idea was created to speed up connections between computers and later Modems / routers / switches by introducing twisted pair and "8P8C" (RJ45) connector to the market. While a "straight" cable is enough to connect a computer with a switch, two "crossover" cables are required to connect two computers directly. There is more because two standards have been created (T568A and T568B), after which we have a crossover cable.