The Five Elements (Wu Xing 五行) are Wood, Fire, Earth, Metal, and Water. They are not material substances but phases of cyclical energy that interact through productive (生) and controlling (克) relationships.
Short answer
The Five Elements (Wu Xing 五行) are Wood, Fire, Earth, Metal, and Water. They are not material substances but phases of cyclical energy that interact through productive (生) and controlling (克) relationships.
In depth
In the productive cycle, Wood feeds Fire, Fire creates Earth (ash), Earth bears Metal (ore), Metal collects Water (condensation), and Water nourishes Wood. This is the cycle of growth and support.
In the controlling cycle, Wood breaks Earth (roots), Earth dams Water, Water extinguishes Fire, Fire melts Metal, and Metal cuts Wood. This is the cycle of restraint that prevents any one element from dominating.
The Five Elements underpin every classical Chinese metaphysical system: Ba Zi (your elemental composition), Feng Shui (the elemental energy of spaces), Traditional Chinese Medicine (organ relationships), Qi Men Dun Jia (chart interpretation), and acupuncture (meridian flow). Mastering elemental relationships is the foundation of mastering Chinese metaphysics.