line weight to reel weight, any significance?

[monkeyrun]

My first year saltwater fly fishing, I landed a dozen or so on the fly. 2 - 3 keepers. I am now hooked.

I am looking to expand my fly fishing experience. I occasionally head out bass fishing with some friends and figured I would try this next. I am leaning towards a 6 weight mid flex orvis rod. My question is - what is the significance of the line weight to the reel weight (i.e. a 6 weight line on a 9 weight reel). Can I use the 6# line on a 9# reel? What will the affects be?

Thank you in advance for your responses.