1. Demeanor Flaws (ex: rudeness, extreme shyness)
Demeanor flaws make it hard for other characters to see a character’s core personality. Sometimes a character will hurt others without meaning to because of their demeanor. It’s easy, when giving a character demeanor flaws, to portray anybody who misunderstands or is hurt by them as shallow jerks who should spend more time with the poor, lovable character. This should not be the case. People are not obligated, for example, to stick with people who are rude to them. Also, doing this makes the demeanor flaw less of a flaw.
2. Personality Flaws (ex: rigidity, hubris, insecurity)
The most common and my favorite to read about. These are generally what people think about when they think of character flaws. Trying to get over one of these flaws is the arc of many a well-written character.
3. Alignment Flaws (ex: zealotry, fighting for the bad guys)
Somebody can be a nice person with no obvious personality flaws and still, for some reason or another, choose the wrong side. Such characters are a good way to add emotional depth to your stories because they need to be out of the way for the protagonists to win, but they are not fundamentally bad people.