If someone you loved has recently passed, you may rest easy knowing that it is possible that your loved one may visit you from whatever awaits us after death. A spirit is described as a manifestation of a person who has recently passed. Though there exsistance has never been 100% proved scientifically, billions of personal experiences are reported pertaining to the sighting of a spirit.
It is hard to speak about spirits because it may not correlate with some of the worlds major religions, but when we reach the truth, nobody knows for sure what happens after we die, but it provides the opportunity to believe in something bigger than ourselves, an opportunity for faith.
Origin: Being that spirits come and go at will, spirits can't be singled out to one background. Spirits are found, in some form or another, in virtually all cultures of the earth.
Appearance: Once again, spirits are the manifestations of deceased loved ones. Their appearance depends entirely upon the deceased features before they passed away.
nfluences on Modern Day: Spirits have certainly plagued the thoughts of scientist for centuries. Spirits also cause the spiritualist movement in 1840's . Some, called mediums, claim to be able to interact with the spirits of the dead and sometimes relay messages to their family members. Today, ghost hunters search in the depths of seemingly haunted houses for proof of the after-life. The time of spirits has never been greater than it is right now.
 Wikipedia.org: Spiritualism