Power Star
Power Stars are mystical artifacts with great power. Unlike the regular Stars, which only give limited invincibility, Power Stars grant the user with great strength. In Super Mario 64 and Super Mario 64 DS games, Power Stars are spread throughout the worlds, and Mario (or in the Nintendo DS remake, Mario, Yoshi, Luigi, and Wario) is sent to go find them all. There are 7 power stars (8 in DS remake) to collect in each world, and after finding 70 of them (80 in DS remake), the final boss, Bowser, can be defeated. There are 150 Power Stars in all, as of Super Mario 64 DS, but only 120 were in the original. After a long quest, Mario manages to find all the Power Stars and restore them to Peach's Castle, freeing Peach and the Toads.
Stars have since been a recurring theme in Mario, but in particular Power Stars are used often in the Mario Party series of games. As of late, however, they have been phased out in favor of Shine Sprites.
However, Power Stars make a return in the Nintendo Wii game, Super Mario Galaxy. Theres four kinds of Power Stars. The first kind is regular Power Stars, the bread and butter of the 3-D Mario Games. Second kind is Green Power Stars, they are like normal Power Stars, there's only three known Green Stars, they unlock the Green Star Shooter. The next are red power stars. There is only one which appears in the Super Mario Galaxy mission "Gateway's purple coins." Lastly is the Grand Stars, gotten from beating Bowser, Bowser Jr., or another boss, these powers up the Comet Observitory.
There are also Silver Stars, which aren't as powerful as Power Stars, but five of them is equal to one.