Imagine you have a bunch of toys, and you want to put them in a special order. You can choose which toy is the most important, which one is second-most important, and so on.
Now, imagine that each toy has a certain number of stickers on it. The stickers can be red, green, or blue. The toys with more stickers are considered more important than the ones with fewer stickers.
This is kind of like a graded poset! A graded poset is a bunch of objects (like toys) that are ordered based on a grading system (like stickers). The objects at the top of the order are the most important ones, and the objects at the bottom are the least important.
In a graded poset, there are rules about how the objects can be ordered. For example, if a toy has six stickers (three red, two green, and one blue), it can't be at the same level as a toy that has only one sticker.
So, just like with your toys, things in a graded poset are organized based on how much "stuff" (like stickers) they have. The more "stuff" they have, the higher up they go in the order!