Yes, they existed. When they first began they were mainly men who robbed and killed people, but the church stepped in and made them swear to protect people and fight for the church. A noble boy began training for knighthood about 7 years old and by the time he was 12-13 years old he was a page for a knight, and at 21 he became a knight. Museums today have sets of armor that belonged to knights. Henry VIII's childhood armor can be seen in the Armor room in the Tower of London today.