This is the ability of connecting to other entities at a higher dimensional level. The connection is through the Chakras and out into the Void. Many think of Channelling as being possessed. Some do invoke the entities, but it is not necessary. Channelling can come as subtle thoughts, very like when one is channelling their Higher Self.
How this companionship with one or more entities is formed is by having the same goals to achieve. One has something in common with the entity. There are many beings that are available for contact. These can be Aliens, Jinn, Archons, Demons, Angels, Elementals, Gaia, Guides, Soul Clusters, etc. All of them can be channelled.
For many, channelling starts by achieving a much higher state of consciousness through meditation. This gives access to the higher dimensions as the Mind crosses the Void. Some raise their vibration. Being on a low vibrational world, this is good advice. One must make their intention clear about what goals they wish to achieve in their life.
When we are born into this life, our Higher Self tries to connect all through it. Most people ignore it, until there is only the self, alone. Once one reaches this condition, it is called, an Awakening. One has now fully connected and become a multidimensional Soul Entity. As time goes on, one will realise that they have a tribe in the Astral Plane.
It is unknown if all have avatars on this Plane, but one thing is certain, it was expected that we would all be isolated and that most Magic would have to be assisted by those in the Astral Plane. All Souls are connected to the All, the Source. All Source is connected to everything. This is channelling. One intends to connect with the Others.
Those who channel entities for certain purposes lasting a long time, will find that the information received will later be proven. One must channel first before then looking at information. This then builds up the relationship knowing that the entities channelled are sending oneself, new information, rather than just telling anything that one would like to hear.