whistle or clicker training?

hi all.. i jus have a quick question...
I started training indie to recall on a whistle a little while after i got her.. and when i kept it up, it worked very well.
However, with her puppy training classes, that started on wednesday, they do clicker training.
What we have been told is :get them to do the action like sit, then once they have done it, click and treat.
I dont understand what this is meant to do? Its not like you will be clicking it for them to come to you. So what effect does a clicker have?

does it jus train them to hold the position without running off??

Have a look in Beahviour and training jenny, theres a dedicated section on clicker training,

my dog trainer doesnt believe in treats and says it should just be hand commands!! i am finding it difficult as max thinks my hands are of no use unless they have something edible in them!!!

lol! @ Katy (rockys the same!)

Yeah Jenny check out the clicker training thread that ROb mentioned, has Loasds info in it

so does everyone agree with treat based training for pups. Max will do anything for a cube of cheese. I think he would do back flips if I held out