Sailor Planet Power was a group command, performed by different groups of Senshi in the anime and manga. This command was quite similar to Sailor Planet Attack.
In the anime, the attack was performed by all five Inner Senshi. It could be performed without Sailor Moon involved, although the command was only half as powerful in her absence. While underneath their target, the Senshi would link hands in a circle and concentrate, combining their powers and sending a burst of energy straight up, in roughly the same manner as Chibiusa's moonbeams in the Black Moon arc of the Sailor Moon R season.
Although the attack was performed similarly in the manga, it was called Sailor Planet Power Meditation (セーラー・プラネット・パワー・メディテイション) when it was first used by the Guardian and Outer Senshi to attack Zirconia in Act 40.