Where your purpose points
Astrology places purpose at the Midheaven — the highest point of the sky at the moment you were born, and the part of a chart describing what you are meant to be seen doing. This works it out from the real position of the sky, then follows every thread attached to it.
Needed for the Midheaven and Ascendant, which depend on where on Earth you were.
North and east are positive; south and west negative.
In plain English
Direction — Midheaven
Fuel — Sun
What sustains it — Moon
Approach — Ascendant
The condition of the whole chart
The two axes your purpose hangs on
What carries it — the ruler of your Midheaven
And the ruler of your Ascendant