You need to clear the game field by filling lines, columns, and 3x3 sections with blocks. You get points for placing blocks onto the game field and for clearing it. The same goes if you manage to remove several lines\columns\sections in a row. You get three new block figures each time you use up all of the given blocks. The game is over when there are figures left in the set but no place on the game field to put them in.
Have fun, gamers ;-)