Humans, like all other living things, are born, live for a while in this world, the only one we have, and then die and rot away. For much of recorded history, humans have imagined various  kinds of existence before birth, and various kinds of existence after death. The simple fact that these imaginings have no detectable counterpart in our real world would seem the final say on the topic, but it is a characteristic of most of the world's religions that some kind of existence outside the boundaries of physical life is taught as an actuality.  Our knowledge of what life actually is, and how incredibly fragile it is, rules out all of these imaginary possibilities, but relatively few people seem able to deal with the blunt harshness of reality.  So there is money to be made in offering "attractive" scenarios, the relative attractiveness being strongly culture-dependent.  Needless to say, pseudoscience has come through splendidly, and there are a huge number of bizarre aspects to the various scams that have been concocted.

The ideas of invisible components of living things trace back to ancient ideas attempting to describe by scenario the difference between the states of life and death. There are nearly as many versions of these invisible components as there are different cultures on earth.

These are the most common versions of the life/death scenario. Cultures such as the ancient Egyptians expanded on these ideas to an incredible degree, partially by combining several originally completely different religions into a single one. One simplification of the Egyptian ideas that has come down to the present day is the Body Double, or Astral Body, an immaterial thing that is otherwise identical to the physical body, and has the same situation, profession and needs as the real body, after the real body dies.
A classic pseudoscientific spinoff from this scenario is the claim that "psychics" can do "astral projection," that is,  send their astral body out to view distant locations and events, as popularized particularly in late 19th Century Theosophy.  This eventually evolved into the pseudoscience of remote viewing.

Once the unverifiable concept of a soul had been introduced, an obvious question arose in some cultures. If the soul was immortal, where was it before the individual was born? Was it conceived and born with the individual, or did it get attached to the individual somewhere between conception and birth? And if attached, where did it come from? This led to a scenario in which a soul, when an individual dies, jumps immediately to another individual being born at that same moment! This is the idea of Reincarnation, or Metempsychosis. The latter doctrine is usually attributed to the ancient Greeks, but the former, general concept is mostly found in religions of the Far East. Pseudoscientists of all stripes absolutely love this concept. You can take (expensive) courses to learn to remember your (many) past lives! Scientology has particularly exploited this theme.

"Who would fardels bear, To grunt and sweat under a weary life, But that the dread of something after death, The undiscovered country from whose bourn No traveler returns, puzzles the will And makes us rather bear those ills we have Than fly to others that we know not of?" (Shakespeare, HAMLET, Act 3, Scene 1)