What is the purpose of amendment 26?

Only the first 10 amendments are the Bill of Rights, after that they are just amendments.

Amendment 26

18-year-old suffrage Section 1. The right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.

Section 2. The Congress shall have power to enforce this article by appropriate legislation.

Ratified June 30, 1971.