A house is a term that
astrologers use to indicate a portion of the sky which the
sun,
moon, and planets travel through. The sky is dived up into twelve houses, just as the sky is divided up into twelve signs.
The houses however are not identical to the signs - the houses may be of different sizes. While the zodiac signs are always 30 degrees, the houses may be less or greater. In the "Natural Horoscope", the houses are all assumed to be exactly 30 degrees in width. This rarely occurs (it happens when someone is born on the equator) but is used as an aid for learning astrology. This type of chart is also used when the time of birth is not known and thus the actual cusps of the houses cannot be determined.
Each house has a meaning - just as the planet represents the what with respect to an event and the sign is the how, the house represents where the events manifest.
The first six houses represent the self - self development, and expression. The last six houses represent others - our relationships, and co-operations. The line between the first and seventh house cusps is the actual horizon, thus the first six houses are visible looking at the sky (known "of the sky") while the last six houses are not visible (know "of the Earth").
Between two houses is a 'cusp' where one house ends and the next begins. These can be thought of as spokes in a wheel. The first cusp appears at 9 o'clock, and the other cusps follow going counter clockwise.
The 12 Houses : 1 2 3 4 5 6 7 8 9 10 11 12
http://www.astrology-numerology.com/
http://www.astrologyzine.com/what-is-a-house-in-astrology.shtml