It consists of a series of disks on which are shown the positions of prominent stars.
Some authors attribute the invention of the astrolabe to Hypatia of Alexandria, based on a misinterpretation of a letter written by one of her students, but it is well established that it had been invented some $500$ years earlier.
Use of the astrolabe was adopted by the medieval Arab world, where its design was made considerably more sophisticated and intricate.
The word astrolabe derives ultimately from the Greek word astrolabos from astron (star) and lambanein (to take).
Hence it literally means star-taker.