To begin with, there must be some basic understanding of energy. Energy is what moves the universe through time. It is what causes all things. Now there are the usual types of energy you learn about in school, (mechanical, solar, electrical, magnetic, etc.). Yet there are other types of energy that science doesnt explain nor does it discuss or even admit to its existence though it is clearly evident if one pays attention to the bizarre. These are what I call, bondable, or creative, energies. When I say creative, I mean as in the forces that created the universe and the energy that connects things together and produces gravity. Magic, Chakra, Aura, whatever you want to call it, manipulates things both through this creative energy. But the ones that take a lot of energy can have the energy consumption reduced through a ritual and the premise of the association of things (which is having a profound belief that any two things are connected).
An example of this is that if you . . . took a piece of glass for instance, say, from a broken beer bottle. Now, though the bottle had broken, the glass shards wouldnt become glass. The beer bottle, like everything else, has a sort of energy signature you could say, and because of this, the piece of beer bottle you have is still a part of the original beer bottle. So then if you know how (which will be covered later), its, signature, could be traced back to the original piece. Thus the concept of a beer bottle can be used to apply energy to something on a small scale, and then have it occur on a large scale.
Now, there are beings outside of our universe, our perception of reality. This is a well-known fact. These beings, like everything else, have energy. The reason they are always perceived as gods and goddesses is that they have figured out how to send their energy into this universe to affect things. And because of energy constantly coming into the universe, you get a sort of current. Animals and plants can feel this current, but because of humanities complex mind, we have sought out where this energy begins, to find its source. We have done this through prayer, meditation, astral projection, etc.. These attempts, which are still going on today, are sending back energy which ends up with you having very sensitive, two way channels of energy running through and out of this universe. That so many outside and inside this universe are transmitting and because of individuals auras (vibrating frequency unique to each person or being), there is no known number of specific currents.
Over time, given a strong enough connection, a being can use energy to manifest a body (which can be made of light, matter, or even in your subconscious or conscious self) with either their whole or part of their spirit which when encountered, causes them to be known. Even though Godden (commonly known as God) is the supreme god-goddess outside this universe, the gods of mythologies around the world (including Egypt, Rome, Greece, India, Aztec, and Druid to name a few) are real and facets of them have been captured as myths, legends, stories, and fables.
Now a prayer to whom or whatever wont necessarily be answered by the specific being you prayed to. If it is answered it might be by something completely unexpected or comprehendible. An answered prayer can be described as an astral neon sign tuned to the right frequency (by frequency I mean purpose, desire, and intent of the prayer) to catch a being or beings attention who then acted upon the astral sign and thus it was done.
Now a summoning done correctly will catch and/or pull the attention of that specific being or state (state is the only word I can use to describe something that has no conscious), so out of curiosity or being forced to, it comes to you and may or may not manifest itself as something, depending on its or your desires.
Now you can also just snag and scoop energy without a being ending up involved.