Think of a level structure like a ladder. You start at the bottom rung and climb up to the top. Each rung represents a different level or stage that you have to pass through in order to reach the end.
In a level structure for a game, you start at the beginning of the game and have to work your way through each level until you reach the end. Each level can have different challenges or puzzles that you need to solve in order to advance to the next level.
Just like climbing a ladder, you have to complete each rung or level before you can move on to the next one. Sometimes, if you can't complete a level, you have to go back down a few rungs to try again until you get it right.
Overall, a level structure helps guide you through a game and gives you a sense of progress as you climb higher and higher through the levels.