How to understand it
A moving planet may cross a natal degree or form an aspect to it. Timing depends on ephemerides and the chosen timezone; slow planets can make several passes around retrograde periods.
An example
Use a transit as a scheduled reflection: review the topic it suggests, then check actual circumstances before deciding anything.
Use it carefully
Avoid using a transit as the sole basis for medical, financial or relationship decisions. Keep practical evidence and consent in view.
Try a reflection
What is happening now that you can verify independently of the chart?