Astrology is a system of divination founded on the notion that the relative positions of celestial bodies can influence human affairs and personal lives. It is a baseless pseudoscience similar to homeopathy in that people believe it on no logical or evidential basis, but possibly only because it is comforting. In this way it is also similar to most religious beliefs. Carl Sagan and James Randi are among the most notable and staunch critics.
"The desire to feel connected with the Cosmos reflects a profound reality: We are connected, not in the trivial ways that astrology promises, but in the deepest ways." - Carl Sagan