The Indian Succession Act of 1925 governs wills made by various religious groups except Mohammedans, outlining key principles such as the necessity of sound mind for will-making and the distinctions between privileged and unprivileged wills. Privileged wills, applicable to certain military personnel, can be oral and require fewer formalities, while unprivileged wills must be written, signed, and attested. Essential components of a will include the testator's identification, revocation of prior wills, appointment of executors, and clear bequests.