"Continual" means something is reoccurring. Examples:
1) The continual attacks on the poor led to a revolution.
2) He continually arrives to school late.
"Continuous" means something is happening without interruption. Examples:
1) He caught the ball, turned around, and threw it all in one smooth, continuous motion.
2) The continuous sound of the waterfall can be heard from a mile away.
3) She has been continuously sending emails since this morning.