In simple words
Your birth chart is fixed. The sky keeps moving. When a moving planet lines up with an important point in your chart, astrologers call it a transit.
The Moon's transits last hours, the Sun's and Venus's days, Mars's about a week. Your Today page finds yours automatically; here you can read any of them.
Sun
To your Sun: conjunction · opposition · sextile · square · trine
To your Moon: conjunction · opposition · sextile · square · trine
To your rising sign: conjunction · opposition · sextile · square · trine
Moon
To your Sun: conjunction · opposition · sextile · square · trine
To your Moon: conjunction · opposition · sextile · square · trine
To your rising sign: conjunction · opposition · sextile · square · trine
Mercury
To your Sun: conjunction · opposition · sextile · square · trine
To your Moon: conjunction · opposition · sextile · square · trine
To your rising sign: conjunction · opposition · sextile · square · trine
Venus
To your Sun: conjunction · opposition · sextile · square · trine
To your Moon: conjunction · opposition · sextile · square · trine
To your rising sign: conjunction · opposition · sextile · square · trine
Mars
To your Sun: conjunction · opposition · sextile · square · trine
To your Moon: conjunction · opposition · sextile · square · trine
To your rising sign: conjunction · opposition · sextile · square · trine