If you've found your way to this page, then chances are, you either have an epic trip in the works, or you're sort of a poser and just want to look cool. It's okay either way. I don't judge. If you are going on a lengthy adventure, then you for sure want to bring an expedition pack with you. When you're gearing up to be gone for a few weeks straight, you'll want to bring pretty much everything with you. Even the kitchen sink, but that probably won't fit in your pack no matter what.
Seriously though, Expedition Packs are made to hold all the gear you could possibly need when out in the field for a couple weeks. Obviously, you'll be able to carry all the normal camping gear like a sleeping bag, tent, stove, food, clothes, water, and what not. However, if you're actually on some sort of expedition, then chances are you'll also have other gear for scientific research, photography, medical supplies, or whatever else badass people do that require a backpack so large.
Expedition backpack research and design has come a long way in the past few years too. No longer is carrying 50+ pounds of gear super uncomfortable. With improved frames and ergonomic suspension systems, these packs aren't only comfortable, but also help to reduce moisture build up on your back with air flow technologies that help keep you both cool and dry. The weights of most expedition packs have also been reduced to pretty much nothing. Gone are the days of the super heavy metal frames. The only thing weighing these backpacks down now is whatever gear you need to keep stored inside them.