In Yoga and Ayurveda, there are five elements which compose the entire universe.
Space (or Ether) -- Akasha in Sanksrit. From which all things come and to which all things return, present in all things, seen and unseen, and the equivalent of the divine.
Air -- Vayu in Sanskrit. Akasha in motion is Vayu. Responsible for all movement, is most present during the change of the seasons and is the best time to cleanse (Spring and Autumn). In the physical body, Vayu oversees the nervous system and mobility.
Fire -- Tejas in Sankrit. Tejas is fire. Responsible for all transformation in the entire universe. Tejas is most prevalent in the body in neural synapses, digestion, metabolism and catabolism, heat management and all change from one form to another.
Water -- Jala in Sanskrit. Jala is flow, cohesion, lubrication, covalence and connection. Water is responsible for the initial connection, such as in egg and sperm, thought to emotion, and electron to nucleus. It keeps fire from getting too hot and incinerating or burning up all that is, and it keeps earth from becoming rigid and brittle.
Earth -- Prithvi in Sanskrit. Prithvi is responsible for all form in the body. It is the most gross, least subtle, and shows up in all mass in existence. It is the furthest from who we are, as is represented in our physical body: the "modified food body" or Anamaya Kosha.
Each element has a sense organ, a finger (on the hand), a "seat" in the body from which we can witness its movement in and out of balance (as we see in the doshas: Vata, Pitta, and Kapha).
Now, see how the elements affect your yoga practice:
Earth element practice is very physical, based upon strength, stability, and foundational practices. Water element practice is flowing, humid, juicy, and sensual. Fire element practice is serious, hot and dry, focused, and penetrating. Air element practice is light, cool, mobile, and light -- with many pranayamas designed to elevate spirits, lighten mood, and raise one's consciousness. Ether element practice is devotional, meditational, spiritual, one with all that is and is rich with bhakti or devotion.