Planets are often said to be “retrograde,” and what this means is that they appear to move in reverse along the ecliptic.
What’s really happening is just a result of our planet’s orbit in relation to another; once in a while an inner planet will “lap” us in its path around the sun, or we’ll speed ahead of one of the outer planets. (Good scientific explainer here.)
There are a few crucial points astrologers care about when a planet goes retrograde.
Entering the “shadow” zone
The planet is still moving forward at this point, but it is now traveling over territory that it will return to during the retrograde. People may begin to feel effects of especially strong retrogrades now. The speed of the planet along the ecliptic begins to slow and will eventually come to a stop.
When a planet stations, it appears frozen at a single point in the ecliptic like a temporary star. After stationing retrograde, a planet will then appear to move backwards through the ecliptic.
From here, the retrograde period has officially begun. To get a sense of how this will feel for a given planet, consider the strongest qualities of that planet — and then imagine second-guessing all of those things. Retrogrades happen most frequently with Mercury, which governs communications… and explains why so many messages seem to be delayed or waylaid during retrogrades.
Here again, the planet is temporarily frozen in place and is now back to where it was when the “shadow” period began. Most importantly, it begins to move forward again from here! Whatever became foggy or unclear during the retrograde period begins to clear up around this time.
Leaving the “shadow” zone
The planet is now on its way through all the territory it crossed during the retrograde, and this is a great point to take stock of the full effect. What feels different now? What did you have to go back and adjust?
A note about modern planets
Uranus, Neptune, and Pluto are considered the “modern” planets in astrology and their accurate observation is a matter of serious scientific progress. Traditional astrology covers only the planets you can see with your eyes; thanks to their proximity, the connection is simply stronger. For this reason, and also because the outer planets move so slowly, I don’t really count down the days of a Neptune retrograde (for example) like I would for Mercury.
My rule of thumb: Unless you’re working with powerful drugs (Neptune), literal dark matter (Pluto), or super-advanced electrical systems (Uranus), you can probably take outer-planet retrogrades in stride.