Refluxing is continually boiling a solvent without evaporation. This is done by using a "reflux condenser" which is a open-ended glass tube with cold water running through the hollow walls. You put the reflux condenser on top of the flask which holds the solvent you are boiling. When the solvent vapors go up into the glass tube, they come in contact with the cold glass (from the circulating cold water inside), and the vapors condense and drip back into the flask. It is a way to boil solvent for a long time without any evaporation and still doing it in an open container. See Web Links to the left for some images and more details.
Reflux is a technique involving the condensation of vapors and the return of this condensate to the system from which it originated. It is used in industrial and laboratory distillations. It is also used in chemistry to supply energy to reactions over a long period of time.
Reflux can also refer to the process in the body where fluids back up and travel in the wrong direction, especially acid reflux, where stomach fluid bubbles back up into the esophagus and burns the lining.
They're pretty closely related concepts. Basically, all refluxation involves condensation, but not the other way around. Reflux is when you heat something to vapor phase, condense it, and allow it to drip back into the pot. Condensation is any change from vapor phase to liquid phase; the condensate might then flow into the original vessel (reflux) or into a separate one (distillation).
equation: CH3CH2OH +4 I2+ 6 NaOH ----> CHI3 + HCOONa + 5 NaI + 5 H2O