The act is called the Voting Rights Act of 1965.
This act, signed into law by Lyndon B. Johnson, helped to remove legal barriers that African-Americans faced when it came to voting. For example, African-Americans were unfair targets of things like literacy tests, poll taxes, and the grandfather clause. All three of these barriers were put in place to limit the amount of African-American citizens voting in local, state, and national elections.
This law ensured that African-Americans received the same protection guaranteed to them under the 15th amendment.
Andrew Johnson extended a general pardon of citizens of the South in the form of the grant of an amnesty, subject to several exceptions: officers or diplomats of the Confederate;those who left US judicial stations to help rebels;those above certain rank, such as Colonel; etc., in general denying the pardon to those who had more responsability in the rebellion.