Telepathy

Telepathy is the communication of messages or thoughts directly from one mind to another. Generally, the images are received and processed by the brain in a manner similar to ordinary sensory input, so in essence a telepath "speaks" and "hears" perceptually. However, the ordinary vocal and auditory mechanisms are not employed. Telepathy exists across space; it has appeared in various forms among various races.

Types
A touch telepath can communicate directly with the mind of another being, but only if in physical contact. The Vulcan mind meld is a form of touch telepathy (although there is more to it than that).

Some telepaths can exchange thoughts only with others of their own species, some can send but not receive, and some can receive but not send. Betazoids, for one example, can send and receive the thoughts of other Betazoids, but can only receive thoughts from alien minds.

In some races, telepathy is present in all healthy individuals (those not born with congenital problems and not the victims of accidents or disease). In other species, such as Humans, telepathy appears only infrequently. And certain species, notably the Ferengi, are never telepathic. Often such species cannot be read even by telepaths normally capable of reading alien minds.

Overview
Telepathy makes possible some forms of interaction that would otherwise be impossible. The Medusans are an incorporeal race so ugly (or perhaps merely so alien) that the sight of them drives humans insane. Interaction with them was very limited, until 2268, when Miranda Jones established a telepathic link with Ambassador Kollos, proving that it could be done.

Extraordinarily powerful telepathic species exist. They are rare, but are extremely formidable, as they can immerse other minds in a realty of their own fabrication, much like a holodeck, but where the telepath makes all the rules. The xenophobic Melkot used their telepathic powers to punish aliens who encroached upon their space without permission (which, prior to 2268, they never extended).

Under rare circumstances, individuals can gain telepathic powers. In 2264, exposure to the galactic barrier altered Gary Mitchell, who developed telepathic powers. In 2266, Captain James Kirk and the starship Enterprise took aboard a passenger, Charles Evans. Subsequent events revealed that Evans had been granted various psionic skills by the enigmatic Thasians, so that he might survive on their world.

Telepathic races such as the Betazoids usually develop a moral code (sometimes making it actual law) that precisely dictates under what circumstances the powers may be used. Telepathy, misused, can be the ultimate invasion of privacy, and for that reason, it is feared by some.

Some telepaths can send and receive feelings and emotions. Sometimes this is part of a telepathic skill, and sometimes it is their only skill. In the latter case, individuals are referred to as empaths. A notable empath is Deanna Troi, daughter of a Betazoid and a human; she inherited a limited form of her mother's telepathic power.

Explanation
Telepathy is possible because the sentient mind itself is independent of the brain. It exist as a field of energy in space and the brain functions by simply "tuning in" to this field like a radio tuning into the energy signal from a station, the DNA serving in a similar capacity. The body's bio-energy field acts as the "antenna", a bridge to the mind field.

This being the case, each mind has its own separate field. While existing in the same space, each field is effectively separated from other minds, by virtue of having a different frequency - one unique to itself. The mind fields exist in a parallel universe. From such a universe all points in this realm are accessible from one location in it and vice-versa. In effect, the mind field can be said to be all-pervasive relative to this universe.

Telepathy is analogous to cordless phones/cell phones and crossed signals. While everyone's physical/energetic signature is unique, overlapping is possible, which allows a telepathic individual to "tap into" the mind field of someone else by "getting into resonance" or "tuning" to that person's bio-energy field signature to match their mind frequencies, allowing for the "sharing" of thoughts and emotions, and, in some cases, even their "programs" (personality traits, etc.) such as in a Vulcan mind meld.

''Incidentally, this also explains the latent capacity for genetic memory in humans: as the DNA is so instrumental in the "tuning" process, people of close genetic relation, thus sharing elements of their DNA, may "tap into" ancestors' memories. Even if an ancestor is dead, their "data" and "programs" still exist in the parallel realm.''