What does a reflux condenser do??

Question

for my chemistry lab of esterfication

Answer 1

If you are heating a reaction with solvent to the boiling point, you want to condense and return the solvent vapor to the reaction vessel so it doesn't dry up. That is what the reflux condensor does.

Answer 2

just an addition beside useful for retaining solvents, for highly volatile reagent like (COCl)2 as well.