Brahmacharya is a widely used term in India and it may be explained in different ways by some Traditions or Gurus. It is very useful to know the literal meaning of this word.
Brahmacharya consist of “Brahman”, Supreme Reality or Absolute, and “charya” that means “following”, “behaviour”, “one who practices or performs something”. That is following Brahman or lifestyle oriented on Brahman, Absolute.
In vedism and brahmanism brahmacharya is the period of life approximately from the age of 10 till 25 when disciple learns up from Guru the knowledge of Vedas, Upanishads etc. in Gurukula (special school).
In many other traditions in India, including the strict sannyasa (and ascetic forms of sadhana), brahmacharya is the celibacy, sex abstinence that, as assumed, will help to direct all intentions of sadhaka to Supreme Reality.
In yoga and tantra brahmacharya is comprehended as control of all sensual activities, especially sexual desire, lust. It’s a perfect retention of energy on physical and mental levels.
Brahmacharya begins with the feeling of measure in all sensual experiences, not only in sex but also in other kinds of enjoyment like eating tasty food, listening good music etc. All these enjoyments tend to carry us away and we loose awareness, control and our bindu — life force. If we want to achieve real progress in our sadhana we should not loose that energy but raise it up to the highest levels of consciousness. Of course it cann’t be done only mentally or physically, for successful transformation of sexual energy we need all parts of Yoga and Tantra: lifestyle, rituals, Guru-seva, hatha-yoga, mantra-yoga and so on.
Brahmacharya is not always and not only the celibacy as it is often said. The most important is to understand that the meaning of this principle is direction on Pure Brahman, and not to worldly enjoyments through which Maya (illusion) manifests. Thanks to our pure intention the sexual energy will gradually change direction to more creative mode, to knowledge. On the highest levels brahmacharya is the activity that have no duality, differences between genders. Brahmachari is one who is always in connection with his Atman, and from this state he can enjoy life, even have sex if it is necessary not loosing his bindu (urdhvareta). Yoga texts teach us — all that we perceive as pleasant and unpleasant, good and bad is Atman. Thus holding our consciousness on this point we find out the nature of all existing things is the only Atman. And when we enjoy things with this understanding (knowledge) we actually feel the great bliss of Atman — ananda — and are not limited to phenomenal manifestations of this world.