It stands for Aqua Design Amano. It is a well known company that makes many plant specific equipment and products such as Aquasoil (a plant specific substrate), glass inlet and outlets for canisters, and plant tools like tweezers/tongs.
They make good stuff but it is usually very pricey. Takashi Amano is the founder and is probably the worlds most well known aquascaper basically pioneering aquascaping as we know it today. He is also credited with the popularity of the Amano shrimp which is named for him which is a well known algae eating shrimp that is beneficial for planted tanks.