The elements (also known as the triplicities) consist of fire signs, earth signs, air signs, and water signs. Generally, fire signs are enthusiastic, earth signs are practical, air signs are intellectual and communicative, and water signs are emotional. People who share a strong emphasis on certain elements are often highly compatible.
The qualities, (also known as the quadruplicites) are cardinal, fixed, and mutable. Cardinal signs are outgoing, fixed signs are rigid in opinion , and mutable signs are flexible and adaptable.
Gender consists of masculine and feminine, or positive and negative signs. Very roughly, people of masculine/positive tend to be extroverted, and people of feminine/negative signs tend to be introverted. However, this group is perhaps archaic and should only be taken tentatively; certainly this is not an indication of masculine or feminine behavior or tendencies.
Each sign has a special relationship with its partner across the zodiac, known as the polar sign. If the sign opposite your Sun sign is strongly emphasized, it will have a special significance in your horoscope. this is particularly useful when comparing two birth charts (thinking perhaps of a personal relationship). For example, if you are Sun-sign Leo, Aquarius is your polar sign. This does not mean that you will have opposite characteristics to a Sin-sign Aquarian, but rather that you will complement each other because of the special rapport and understanding between you. Although you will not necessarily agree, you are likely to understand each others motives.