A power bank is really a rechargeable battery that can transfer power to other Digital devices. Power banks are like wall outlets that you normally takes with you. Simply just plug inside your phone or laptop via a regular USB-A or USB-C cable, and increase, you have prompt portable power. https://modernsmarthealth.com/product/computers/power-bank/battery-capacity/15001-20000mah/baseus-20000mah-power-bank-quick-charge-3-0-usb-powerbank-qc3-0-fast-external-battery-charger-dual-usb-type-c-portable-charger/