Graphology is the study of handwriting, especially when employed as a means of analyzing character and personality traits. The people who practise it will often claim to be handwriting experts. They are not. Real handwriting experts are actually known as forensic document examiners, not as graphologists. Forensic document examiners consider loops, dotted "i's" and crossed "t's," letter spacing, slants, heights, ending strokes and so on. They examine handwriting to detect authenticity or forgery i.e. is that a real signature on a document?
Graphologists examine the same things but for a different reason. They believe the loops, dotted "i's" and crossed "t's," letter spacing, slants, heights, ending strokes and so on are physical manifestations of unconscious mental functions. In other words, they believe handwriting can tell us about personality, aptitude and attitude. It doesn't. Unfortunately, there is no evidence that the unconscious mind is a reservoir of truth about a person, much less that graphology provides a gateway to that reservoir.
Graphology is claimed to be useful for everything from understanding health issues, morality and past experiences to hidden talents and mental problems. However, in properly controlled, blind studies, where the handwriting samples contain no content that could provide non-graphological information upon which to base a prediction, graphologists do no better than chance at predicting personality traits.
The techniques of these "experts" are really nothing more than guesses or deductions based not so much on such things as the pressure exerted on the page, spacing of words and letters, etc but rather the content of the writing itself and background information about the writer. Though graphologists deny it, the content of the writing is one of the more important factors in graphological character assessment. Likewise, it is easy to offer up an analysis of the handwriting of a famous person about whom much information is already in the public domain. If handwriting can really tell us so much then the blind studies mentioned earlier should have no trouble backing it up. The fact that they don't and worse, that any one of us can have the same kind of hit rate in these studies that the so-called handwriting experts have tells us all we need to know.
Graphology is another pipe dream for those who want a quick and dirty decision making process to tell them who to marry, who did the crime, who they should hire, what career they should seek, where the good hunting is, where the water, oil, or buried treasure is, etc. It is appealing to those who are impatient with such troublesome matters as research, evidence analysis, reasoning, logic, and hypothesis testing. If you want results and you want them now and you want them stated in strong, certain terms, graphology is for you. If, however, you can live with reasonable probabilities and uncertainty, you might try another method to pick a spouse or hire an employee... like flipping a coin.