The Orb can peer into other dimensions and other worlds, automatically detect and locate the use of powerful magic, and reveal any great evil threat to the world. Especially powerful mystical forces have, in the past, been able to cloud the Orb. The Orb can be used as a gateway for the viewer to enter into the dimensions it displays. It also seems to be dimensionally linked to the Eye of Agamotto. Individuals entering the Orb can at times exit through the Eye and vice versa.
Strange Tales #118 (1964)
Description of powers (The Official Handbook Of The Marvel Universe Mystic Arcana: The Book Of Marvel Magic #1, 2007)
The Orb of Agamotto is the largest of the "Three Eyes of Agamotto", which also include the Amulet of Agamotto and the Eye of Agamotto. The Orb is utilized by Dr. Strange to view events on Earth and in other dimensions. It can also access the realm of Agamotto.