A portable charger is a charger that you take with you. Charge it at the airport before the flight or at home before you leave. Most portable chargers provide enough power to run devices a few times.
For a tablet, phone, e-book reader, or another device that charges over USB, a USB battery is all you need. Some have multiple USB ports to charge more than one device at the same time.
To charge a laptop on the plane, bring a portable laptop battery charger. Not only do laptops require more power than a battery charger meant for phones, but you need a way to plug the laptop into the charger. A portable laptop charger has the two-pronged or three-pronged connection needed to mimic a wall outlet.