The reason that the upstream speed in ADSL is generally much less than the downstream rate is due to this fact. In the downstream direction, the high frequencies still attenuate, but at the customer end, they have a better chance of avoiding crosstalk since most customers don't have large bundles of wires in their premises. Attenuation is signal loss due to the diminishing signal power as a signal traverses its path. This is a natural part of signal transmissions and signal repeaters may be used to boost signal energy along a path. If the signal becomes too weak, the far end may be unable to recover it.
Crosstalk refers to interference between channels.
In the xDSL world, the interference between nearby cables can have a negative impact on the affected cable. That is an effect of crosstalk. Typically, your computer will need a 10Base-T Ethernet adapter which connects to a DSL device. Depending on your provider, the DSL device is a bridge, router, or both. Most phone companies install separate DSL circuits to customers' premises to separate out voiceband transmissions.