Nymph or streamer techniques

[Steven]

I have seen the word "swing" used several times. Does this refer to when the nymph is moving from the side of you to directly down stream. Sorry for all the questions I am trying to soak it all in.

Yes.

Typical wet fly tactics would be to cast across or slightly down stream and let the current swing the fly down stream of you.

Imagine you're casting to slower water with faster water between you and the target drift lane. If you don't mend, the faster water will put a downstream belly into the line, forcing the fly to speed up and "swing" until it is downstream from you.

If you want to slow the swing, mend line upstream. To speed up the swing, mend line downstream.