Every year, the Sun returns to the exact position it held the moment you were born. Wooly finds that instant — down to the minute — and casts your chart right there, from where you live now. Not a guess about your year: a real sky, calculated.
Once a year, the Sun returns to the exact ecliptic position it held the moment you were born — to the degree, the minute, the second. Cast a chart for that precise instant, from where you're actually living, and you get a real astrological snapshot of the year ahead: not a guess, a calculation.
It's the same idea as your birth chart, just re-cast every year at that one recurring moment — which is why the classical tradition treats it as a genuine reading of the year, not a repeat of your natal chart.
A solar return's houses — which areas of life each planet touches — depend on your location at the moment of the return, not your birthplace. Move across the world and your solar return chart changes with you, even though the sky itself is identical. That's deliberate: this reading is about the year you're actually living, wherever that is.
Curious about the sky at your birth instead? The free natal chart reads that one moment, once — this reads the one that repeats every year.