Everything is energy. If you put your mind to a task, you can accomplish it. An example of directed energy.
Thought is energy, speech is energy, ideologies have energy. Some people are more intuitive than others, empaths. Empaths, through gift and refinement, can feel and understand energy. So a tarot reader is an empath who has studied the symbology of the tarot deck. The minor arcana of the tarot deck represents passion, thoughts, work and emotions. Wands, swords, pentacles and cups are similar to suits in playing cards, from Ace to King. The energy from the major arcana cards such as The Magician, The Tower and The Lovers are weighted more heavily (ie: face cards that carry more power). Each card of the major and the minor arcana represent a state of energy.
The cards can be used to define the states and cycles of the spiritual journey, general readings or readings to understand a specific situation. Energy is fluid, so readings can represent what has happened in the past, present or future. So a tarot reader flips cards into a spread and uses the symbology of the cards to help understand the energy they are receiving. Three things really got me interested in tarot:
when I realized that the cards helped me to recognize areas of my life where I routinely get stuck, either in my emotions or my thoughts
through practice, it has helped me to become more intuitive
it has helped me understand and balance my energies
Remember a good tarot reader is just reading the energies that are being put out. It is through our free will that we decide where to spend our energies.