Falsification is the act of disproving a theory. See Falsifiability. Falsification in the sense of forgery should not be confused with Karl Popper's idea of Falsifiability in Philosophy of science.
Falsification is the act of producing something that lacks authenticity and passing it off to other people as authentic.
Falsification can be a profitable activity, but most jurisdictions consider it a crime called forgery.
Many objects can be falsified. Copies of art objects, such as paintings, have been circulated as though they were the original. Photographs have been modified to suggest something that was not actually in front of the camera. Money has had a long history of falsification. Expensive watches and gemstones also get falsified. Official documents are routinely falsified.
Entire fields of expertise have grown around the problem of ascertaining that something is indeed authentic.