Bandhas are locks that we create within our bodies. The Sanskrit word for bandha means to “hold”, “tighten” or “lock.” These locks gather up energy which would otherwise be dispersed. Bandhas have an effect on the physical and psychic body. It is said that by locking or contracting certain muscles on the physical level a subtle process of unlocking goes on simultaneously on the mental and energetic level. They are associated with energy centers in the spine and brain.
They are practiced together or individually at specific times during asana, pranayama, mudra, visualization, and meditation practice.
There are four bandhas: Jalandhara, moola, uddiyana and maha. Maha is a combination of the first three.