The beings who are known as Q.
The Q Continuum is a realm of near-omnipotent beings, who are known simply as the Q and who appear to live outside the normal rules of time and space. They can reshape reality at will, travel instantly, and take any form they choose, and they regard the lives of mortals with a mixture of curiosity and contempt.
Their society is a strange one. Its members have lived for so long that boredom is a constant danger, and their conduct often reflects it. Some of them amuse themselves by interfering in other civilisations and testing their capabilities, which is one way they pass the time.
The best known member is Q, who first confronts Captain Picard in the episode Encounter at Farpoint and tests humanity as a species. He returns many times, including in Q Who, which introduces the Borg, and in All Good Things, the finale of the Next Generation. Q also appears in Deep Space Nine and Voyager, and he returns once more in Picard.