Just as the word yoga is one of wide import, so also is prana. Prana means breath, respiration, life, vitality, wind, energy, or strength. It also connotes the soul as opposed to the body. The word is generally used in the plural to indicate vital breaths. Ayama means length, expansion, stretching or restrain.
Prana has been described as liquid light, or the energy that unites the universe (the fundamental building block of all things). It is through control of our prana that we achieve union with the divine (prana is believed to be the building block of matter itself so it also connects all things). This union is also known as yoga.