Solar return
Definition
A solar return is the chart cast for the moment the Sun comes back to the exact zodiac position it occupied at birth. This usually happens within a day of the birthday but rarely on the birthday itself. The chart is read as a one-year cycle: from one solar return to the next, the configuration of houses, angles, and planets is taken to describe the symbolic weather of the year for the chart-owner.
In context
If your natal Sun sits at twenty-three degrees of Libra, your solar return for any given year is cast for the precise moment the transiting Sun returns to twenty-three degrees of Libra. The houses of the new chart depend on where you spend that moment, which is why some astrologers travel for a solar return: the same Sun position over a different location places it in a different house. The technique gives a year-shape on top of the natal chart.
To go deeper
The solar return is the best-known kind of return chart: