Al-jawab billahi at-taufeeq (the answer with Allah's guidance)
According to the Fiqhi Usool (fundamental principles)
"Al Waajibaatu Talzimul-Mukallifeen" (Obligations obligate the morally responsible i.e Buloog, attainment of maturity and 'Aql, sanity).
1) To be Baligh, (to be physically matured) is one of the conditions that make Salah, Zakah (and must be Sahib-e-Nisaab (Minimum amount required for Zakaah to become Fardh)), Sawm (fasting) and Hajj compulsory.
2) The signs of Buloogh (maturity) in the case of a male, is when wet dream, growing of beard etc, appear. If there are no signs, then from the age of 15 lunar years.
In the case of a female, it begins at menses or if there is no menses then at 15 lunar years.
