There are two types of wireless charging -- loosely coupled magnetic resonance and tightly-coupled inductive charging. Both are based on the same science of creating a magnetic field through which power can be transferred between devices using the same frequency.

The Qi standard developed by the Wireless Power Consortium (WPC) enables inductive or pad-style charging.

Of the millions of consumer devices with wireless charging capabilities on the market, nearly all were built with the Qi standard.  Popular devices that feature Qi technology include the Google Nexus 4, 5, and 6 smartphones, Google's 2nd generation Nexus 7 tablet, LG G4, Samsung Galaxy Note 5, S6, S7, and a number of models in Nokia's Lumia lineup.

PMA is a competing wireless charging technology which requires a more tightly coupled link between the charger and device.  PMA based charging technology can also send and receive data, so that, for instance, a PMA equipped location like Starbucks could be able to identify mobile devices charging in its cafes and target users with specific advertising in addition to potentially collecting other data.

In contrast, the Alliance For Wireless Power (A4WP)-developed "Rezence" magnetic resonant wireless charging spec allows for a loosely coupled power transfer -- meaning multiple devices can be placed on a charging pad and moved around with little affect to the charge, but at the cost of overall efficiency.

MobilePal wireless power banks support the Qi wireless charging standard, as do MobilePal's wireless charging receiver cases for the iPhone 6 and iPhone 6 Plus. Future wireless receiver models may support dual mode Qi+PMA charging.