A prophecy consists of divinely inspired words of writings, which a person recives through revelation from the holy ghost. The testimony of jesus is the spirit of prophecy. (Rev 19:10).
A prophecy may pertain to the past , present or future.When a person prophesies,he speaks or writes that which god wants him to now,for his own goog or the good of others individuals may recive prophecy or revelation for their own lives.
But test them all; hold on to what is good, reject every kind of evil.