The cosmology of India describes our universe as having fourteen parallel realities on multiple levels, all existing and intersecting within the material realm in which we are currently living.
One of those levels is called the Deva realm. The Deva realm is supposedly the home of the beings who actually conduct the laws of nature to which we are subject. This view of Divine helpers is much misunderstood as the so-called many gods or also as demi-gods, but in India they were never viewed as God, gods, demi-gods or in competition with God. They were, instead, viewed as souls (or more accurately atmas) like us, but living on another plane of material reality and performing specific jobs as administrators of the laws of nature. So, gods is the wrong word for many reasons, the main one being it implies 'God,' which is not an Indian word in the first place. These beings are called Devas, meaning beings who 'work in the light' assisting the Supreme Being by enforcing the laws of nature that allow the universe to function as it does.
Different yet similar to us, Devas are viewed in India, by analogy, much as someone who works in the passport department giving out visas. Devas give out the passports (enforcing the laws of Nature) and we are people using and receiving the passports (obeying the laws of Nature).
It was always the view in India that there are other dimensions of intelligent life in our universe who communicate with humans and that the Devas specifically are the intelligences operating behind the laws of Nature. But the Vedic culture wouldn't have described these beings as aliens in the way we currently think of aliens, as coming from another planet in a metal ship, parking their ship (or crashing their ship in Roswell) et cetera. The Vedas describe infinitely multiple universes filled with many Earth-like and other diverse planets and many kinds of intelligent beings living in these other dimensions, some in contact with this realm.
The closest modern analogs are found in some of the theories of quantum physics, one being string theory, which suggests there are something like eleven parallel realities that are running simultaneously with ours. This idea in physics, of parallel realities crisscrossing, is undeniably reminiscent of the ancient teachings from India.
Finally, beyond these many material realms, the Vedas state that there is an eternal Transcendental realm or abode which, though non-material, makes periodic visits to our physical plane here on Earth. The Transcendental is not considered a material realm and thus represents yet another form of visitation that sometimes takes place. In the Vedas, these intentional visitations from the Transcendental are called Avatars – literally the descent of higher beings from the Transcendental to the material realms.