The king is lesson 4 of 6 in How the pieces move, a basics course suited to players rated around 150 (complete beginners). The king is the most important piece, but a slow one. It has 2 interactive exercises: 2 star-collecting exercises. You play every move on a board and get feedback straight away. The lesson is free.
What this lesson explains
The king moves one square in any direction. If your king is trapped, you lose the game, so keep him safe!