A backpack is a bag that people wear on their back for carrying things. It usually has straps and pockets.
You've probably seen kids or adults using backpacks to carry their books, laptops, and other stuff when they're going to school or traveling. Some people use backpacks as luggage when they go hiking or camping because it's easy to move around with a bag on your back. Backpacks come in different sizes and styles - some are big and bulky, while others are small and stylish.
A knapsack, sometimes mounted on a light frame, but always supported by straps, worn on a person’s back for the purpose of carrying things, especially when hiking, or on a student's back when carrying books.
