What is the difference between mono line and the florocarbon line?

Monofilament characteristics differ from fluorocarbon lines in several ways. Some important things are:

Mono is less abrasion resistant

Mono has a tendency to float

Mono stretches more

Mono is more visible underwater

Mono has slightly more memory

Fluoro is very abrasion resistant

Fluoro sinks

Fluoro does stretch, but not quite as much as mono

Fluoro is less visible underwater

Fluoro, in some brands, is stiffer than mono.

This may not be ever characteristic, but it'll get you into the ballpark as far as know the differences. Do a search here for more in-depth analysis.

Great summary by Crestliner2008 - all I can add is that flouro is probably the better line for "underwater" applications (since it sinks), mono is better for topwater (since it mostly floats), BUT the big difference is that flouro is MUCH more expensive.

Because fluorocarbon is denser, it is much more sensative, making it ideal for finesse techniques like dropshotting, and also for throwing any baits on the  bottom.  It allows you to feel whats down there.  Also, it will bring plugs a bit deeper than mono.  Mono can be useful when throwing treble hook baits because it acts like a rubber band and fish can't throw slack in the line as easily.  This makes it harder to throw your hook.  Also it is good for topwater because it floats

OK thank you all for your replies. Will have to try some

You might want to check into some co-polymer lines.  I think that is great stuff there.  Yo-zuri, and P-line.