Trasmission Speed Vs Bandwidth

There is a correlation between the 2. Ultimately the higher bandwidth a copper cable can support, the greater the potential for throughput (or transmission speed).

I say correlation because I don't know the technical specs of cables well enough to say its causation, but I suspect it is.  There are many variables in cable types (shielding, twist ratios, etc) that are about reducing noise/crosstalk that effect throughput as much transmission bandwidth.

Transmission speed is the measure of how fast you can send electrical signals down the cable. Bandwidth is actual data sent, as a result of using various encoding techniques to have electrical signals represent bits of data.

Without getting too deep in the technicalities, Hertz/Megahertz (Mhz) refers to the rate at which you can clock data on the cable. Various factors impact this like insulation/conductor separation, twist rate, wire gauge, length, etc.

Data is encoded by using some form of signaling to signify 1's and 0's, (bits). You cannot signal/send bits faster than the clock rate the cable can handle, otherwise you will likely get some form of data loss.

Ethernet uses various encoding techniques to maximize the ability to send data over a cable that can reliably support a 100Mhz clock. E.g.: 10Mbps Ethernet uses Manchester Encoding, 100Mbps Ethernet uses MLT-3 Encoding.