What is a Bottleneck in PC terminology?

[Crispy]

That's all I want to know

[DocClock aka MadClocker]

usualy the point at which some device, or software bogs down the rest of the system...just like a highway with 4 lanes merging into 1 lane, at the point of the merge,every car slows down, and thus creating a "bottleneck"...even if the traffic returns to 4 lanes, the bottleneck still exists, and the "thruput" will be slow.
That is the simple'st way I can describe a "bottleneck"
Hope it helps