they both need to use cue to shoot the ball to the hole, but
it's differnt in rules, not "smaller version".
in brief description:
when playing Billiard ur objective to gain points by shooting in
balls, or snooke ur opponent to make him lose points. you need to
shoot a red ball then u get the chance to "eat" coloured balls with
higher points.
in pool, your objective is to shoot in the black color "8" ball.
but before that u must shoot in the set of 1-7 or 9-15 balls.
more detailed rules u just go play with someone who knows, they
will teach u.