Transit
A transit is the aspect a planet in the sky right now makes to a position in a birth chart, and it is the main way astrology describes timing.
The birth chart does not move; the sky does. When transiting Saturn reaches the degree of a natal planet, the tradition reads it as that part of the chart being tested, and the slower the transiting planet, the longer the period.
Speed is what separates a transit worth noting from one that passes unnoticed: the Moon crosses a natal point every month, Pluto perhaps once in a lifetime.
Frequently Asked Questions
How long does a transit last?
From hours for the Moon to a year or more for the outer planets, and longer when retrograde motion brings a planet back over the same degree.
Do transits predict events?
We read them as timing and tendency. Nothing in our reports claims an event will happen.
See also
See this concept in your own chart: Free birth chart