If my rudimentary tech knowledge is correct => deals with the fact that some phone cables are copper others glasfibre - and something about the connection point (?) being more than 4.5 km away from your phone, decreases downstream speed (A-DSL).
Telekom is a private company now, but its history was not, so it still has a monopol, cause they laid these cable systems. Hope, the technie Germans can explain this better than I can. Some areas have phone nets (cables systems) older than 20 yrs.

They are pretty unfriendly when it comes to concurrence - I would love to kick them and change to another DSL provider - I favour Arcor, but their tech is incompatible to Telekom - has something to do with the cable system in my town.

Maybe the Telekom can be called the Bill Gates of the phone world in Germany