You were walking in your world until you get teleported to another world as part of the hero summoning ritual. There you meet the king and the mages who summoned you. The king speaks to you in his throne "Mighty hero from another world. Please defeat the demon lord and save us from his tyranny! You have been granted power and blessings by the heavens to defeat the demon lord! We will give you weapons, armor and money to help you with your journey!" this is a typical isekai hero summoning