Fastpacking is when you go hiking and camping, but you move really quickly to cover more ground in less time. So imagine you're going on a walk in the woods, but instead of walking slowly and taking breaks, you're going to walk as fast as you can while carrying all your camping gear with you.
You'll need special gear that's both light and strong, like a lightweight tent and sleeping bag, and sturdy hiking shoes that won't wear out quickly. You'll also need to be really organized and efficient when packing, because you don't want to be carrying any extra weight that you don't need.
The goal of fastpacking is to see as much beautiful scenery as possible while also challenging yourself physically. It can be really fun, but it's also important to be safe and prepared. So before you head out, make sure to plan your route carefully, bring plenty of food and water, and tell someone where you're going and when you'll be back.