The concept is simple, it is use case based, and then the packing sequence is last in first out (LIFO).
First of all, let's demonstrate the LIFO principle. Let me use the tent as the example, when you pitch the tent, the very first thing is to put down the footprint, and then the inner mesh, the outer shelter. According to the LIFO principle, therefore the outer shelter shall be placed at the bottom of the tent bag, and then the inner mesh, and finally the footprint is on the top.
The above shows how a particular system should be packed. And we shall extend the LIFO principle to the use case. When we arrive to a particular campsite, the very first thing you will do, is probably to setup the shelter/fly... and then to pitch the tent, put all the stuff that belongs to the tent inside, like your sleeping bag, the sleeping pad, the air pump if you use one, the small camping lantern, etc. After doing so, you might want to roll out your camping table and the chair under the shelter, take out your cooking system, the food, etc. Here, shelter/fly is a use case, sleeping is a use case, and cooking is another one. You then pack those systems according to your use case, and the sort then by the LIFO principle.
Therefore, when I pack my camping backpack, I will put in my cooking system at the lowest bottom, or my sleeping system at the lowest bottom, depending on whether I will cook first or not. The camping chair and table should be at the lower part of the backpack. And those at the top should be the shelter, fly or my tent. And the one on the very top should be the lighting system, if you arrive the campsite at night. And the hydration system should be on top as well, given the water source might come before you arrive the campsite.
Camping involves a big backpack, and the stuff inside could be rather messy. Packing them according to the use case is always good so that you will always know where a particular items will be. We won't want to drag everything out just to find a single item from your backpack in the wilderness. Keeping things organized will help you to avoid leaving an important item at home