A horoscope is calculted upon where the celestial bodies were on the sky upon the perspective of your birth place.
The eight plantes (plus Pluto), The Sun, The Moon and other celestial bodies like Chiron make up the representations of urges and needs within us.
The twelve signs of the zodiac occupy 30 degrees each of the 360 degrees sky. The signs describe what will be expressed, the houses where this expression will take place. The houses are also twelve and each house represent different parts of life – values, travels and so on.
Then there are the aspects. Aspects are angles and refer to the positions of the planets. An oppostion is two planets at a 180 degrees distance. A square is 90 degrees and a trine is 120 degrees, parting the sky in three. A conjunction is 0 degrees. Aspects show how the planets communicate.
The ten main celestial bodies make the basis for a horoscope. Here is a blank natal chart, with the houses numbered 1-12 and the 12 signs surrounding them. All that is missing in the planets – information you can calculate by entering the birth time and birth place into a database such as astro.com to draw a natal chart.