Telepathy is the the term used to refer to the ability to transmit and receive information from another being by other means than known sensory communication i.e., verbal or physical interaction. Whilst this is usually considered to be a form of thought transference, it can range from simple emotions or feelings emanating from animals, to concepts, words and sentences produced by human beings.
There are various degrees of telepathy, starting with empathy which is the ability to feel the emotions of others and understand that emotion, sometimes to the extent that it feels like your own, however, Empaths do not always progress to becoming Telepathic, and Telepaths do not always feel empathy with animals, people or the world around them, both may prefer to shut out the mental or sensory noise except when it is absolutely necessary.
The most common occurrence of telepathy may be exhibited by close friends or family members, especially or other children of multiple birth who even or especially when separated and raised by different families in locations miles apart, will exhibit unexplained knowledge of their sibling or when reunited after years without prior meeting, have similar hair styles and dress code or experience the same emotions, stress and concerns at the same time as their sibling even when they have no knowledge of their existence.
Despite many scientific tests and attempts to debunk Telepathy, there is no doubt that some people are capable of knowing our thoughts when directed to focus on an individual, even when not present in the room. This mind to mind communication is difficult to prove consistently to the satisfaction of the regular scientific community.
In the parapsychology world, telepathy is considered to be a potential example of psychic ability and Zenner Cards became a popular method of testing followed by the Ganzfeld experiment but in psychiatry telepathy is considered to be a symptom of psychosis!
The following videos include demonstration, discussion and methods of testing for telepathy.
Telepathy at Wikipedia
How to Develop Telepathy at WikiHow