Pranayama is the combination of two Sanskrit words (Prana and Ayama). Prana is the life force/vital energy, and the fundamental basis of what it is, it was, and it will be, and Ayama is to control. Therefore, the word Prayama is the process of controlling the Life Force/Vital energy.
In other words, it is a unique technique of controlling the breath. Breathing is the combination of inhalation and exhalation, and also a process to balance the body, calm the mind, and energize the body.