A Power Bank isa portable charger designed to recharge your electronic devices when you're on the move. Ranging in size from slim, pocket-sized devices up to larger, higher-capacity Power Banks – they can be used to charge smartphones, tablets etc.
The Romoss Sense 8+ is indeed a good buy, with its massive battery capacity, Fit-charge technology, and very reasonable asking price, not to mention the ability to charge multiple devices at the same time. You can charge the powerbank fast using a QC3.