Each card (especially in the Rider-Waite-Smith tradition) is tied to an astrological sign or planet. For example, The Star is Aquarius. The Tower is Mars. Knowing these adds a layer of predictive timing to your readings.
Consider this: A single red rose appears on multiple cards. On the Magician, it represents blooming potential. On the Death card, it represents the purity of a new beginning. On the Fool, it represents the innocence of the present moment. Without understanding the symbol of the rose (divine love, sacrifice, and unfolding mystery), you miss the nuance. tarot cards the hidden symbols explained pdf