A king is the male ruler of a country or empire. Kings and queens are born or married into their positions, not voted in by the people. You cannot choose to become a king.
Knights were "gentleman soldiers", a kind of noble warrior who lived a long time ago in Europe. They wore plate armour, carried a sword, and rode a horse.
A Queen is the female ruler of a country or empire. You can become a Queen either by marrying a King or by being born into the position, not by being voted in by the people. You cannot choose to become a Queen. A man cannot become a King by marrying a Queen, he simply becomes a Queen's consort, and a woman who has become Queen by marriage stops being a Queen when her husband dies.
