In a typical home game, the PCs are all the same level and face challenges tailored to their level. In an organized play environment, there needs to be more flexibility so characters of different levels can participate smoothly in the same adventure.
Each adventure lists the character levels that are eligible to play it, as well one or more level ranges within the adventure. If an adventure has more than 2 level ranges, each table must choose 2 adjacent level ranges for that adventure. Only characters of a level that falls within those two level ranges can play in that adventure at that table.