In general, effect is a noun, and affect is a verb (viz. Aura's definition).
However, both can be used as verbs! "To effect" means "to put something into effect (action)".
"This information will affect our experiment" = the information will influence the results of the experiment.
"This information will effect our experiment" = the information will be used to get the experiment started.
Even good native English speakers get tripped up by this one.