Organic chem

I was just revising halogenoalkanes and alcohol reactions and had some q's:
1) can someone please explain what reflux is? because it doesn't make sense in my textbook

It's the continuous boiling of a reactant mixtures; this is so ensure that all the mixture reacts, and that no reactants escape via evaporation

2) why do you have to use warm aqueous sodium or potassium hydroxide for bromoethane to be hydrolysed?

If it's not aqueous, than the 0H- ion will act as a base, and an alkene will form
thankyou in advance

I think thats right

Reflux is where in a reaction that is being heated any water lost as water vapour is condensed straight away to avoid the reaction boiling dry.
As for the hydroxide, the OH group is needed as a nucleophile, so due to its lone pair it is attracted to (can attack) the C-Br bond which is polar.