Brahmacharya means "walking in Brahma" or "walking in the creative force of God."
This is commonly translated to mean celibacy, but it does not mean only that. It really means preservation and cultivation of the creative life force, the sexual energy, which can be either in celibacy or in tantric sexual relations. These two modes of behavior produce the same outcome, for both involve preservation and cultivation of sexual energy upward into the divine processes rising in the nervous system through advanced yoga practices.
It is recommended that you establish a solid foundation in meditation before engaging in tantric practices. To read from the beginning of the "Main Lessons", click on the link above.