This four temperaments model is useful for describing broad, general attitudes that people are characterised by. It's quite old, and not very accurate, though it can still sometimes be somewhat useful!
The four temperaments were devised in ancient times, when it was thought that our personalities were caused by a balance of four fluids - or 'humours', as they were then called - in our bodies: blood, phlegm, black bile and yellow bile. This is where the temperaments got their archaic and rather gory-sounding names!
It's nonsense, of course; our natures aren't the result of a balance in our juices. Still, while the cause was horrendously misunderstood, the actual categorised observations can still be seen in people these days.
This system uses four temperaments, which I'll describe below. They roughly describe the general impression that a person gives off, and their approach to situations. They're based around traits that are described and categorised much better by the other personality systems on this site, but the temperaments can be a basic starting point to work from.
The Four Temperaments
These are the four temperaments in their raw, most basic form. It's important to see these as wholes; you have to connect the dots and look at the big picture rather than seeing individual traits in isolation.
Sensitive, serious, perfectionistic introverts. They tend to have a dour disposition.
Calm, unassertive, peaceful, accommodating introverts. They dislike pushing themselves forward.
Dominant, aggressive, forthright, assertive extroverts. They prefer to be in charge, and challenge others freely.
Boisterous, lively, attention-seeking extroverts. They tend to be openly emotional and cheerful.
Personally, I use temperament blends rather than each temperament in isolation. It's less one-dimensional this way, and you end up with twelve types rather than just four.
These blends have a primary temperament and a secondary temperament, for example 'Melancholic/Phlegmatic' or 'Melancholic/Choleric'. The primary describes the main form of the person's nature, while the secondary adds colour and detail.
Each blend is a separate type in itself, like how red/blue would be purple all of the time rather than 'half blue' or 'red sometimes and blue other times'.