While some backpacks are obviously designed for more strenuous outdoor activities, most backpacks can also double as backpacks for books. When it comes to the subject of backpacks, there really isn't much difference. The two can be used interchangeably to describe the popular school backpack. A backpack is a bag with a strap or handles that is spacious enough to carry books and other items.
Merriam-Webster defines a book bag as “a bag or sack that often has a handle or strap that is used to hold books and other items. In conclusion, both backpacks and backpacks are types of bags that can be used to carry things, but they have some key differences. Backpacks are usually smaller and have a single compartment, while backpacks are larger and have several compartments. Backpacks also usually have a frame, which helps to distribute weight more evenly and makes them more comfortable to carry.
Backpacks often carry school supplies, such as textbooks and notebooks, or work supplies, such as laptops and other electronic devices. Typical school backpacks generally lack the rigid frame of an outdoor backpack and include only a few pockets on the front, in addition to the main storage compartment. The most common examples are backpacks for small valuables, such as laptops and cameras; backpacks specially designed for laptops usually have a padded compartment for storing the computer and medium-sized pockets and flaps for storing accessories such as charging cables and mice. They're not big enough for the average backpacker who uses full-size sleeping bags and backpacking tents, but they can be big enough for ultralight backpackers.
The backpack with internal frame is a recent innovation, invented in 1967 by Greg Lowe, who later founded Lowe Alpine and Lowepro, companies specializing in backpacks and other types of carrying bags for various equipment. The design of the backpacks took another big step forward with the presentation of the first aluminum backpack with external frame by Jack Abert, an avid hiker from Phoenix, Arizona.