[c-nsp] What does "Tx-Bytes-Queue-X" mean in "show interface Gix/x counter details" output?

[Martin T]

I have an WS-C4506 switch with WS-X4448-GB-RJ45 linecard. If I execute
for example "show interfaces Gi6/1 counters detail", I'm able to see
counters in all queues:

Port       Tx-Bytes-Queue-1  Tx-Bytes-Queue-2 Tx-Bytes-Queue-3  Tx-Bytes-Queue-4
Gi6/1        10504791180515       29027243249       7968546934        1520451587

Why aren't frames equally divided between those four queues? Why are
there four queues?

regards,
martin