Question

The focus of most international efforts on fuel cells is on PEM and SOFC

Answer 1

PEM is Proton Exchange Membrane and SOFC is Solid Oxide Fuel Cell. These are efficient and can be used at a large scale. 
PEM fuel cells use hydrogen and oxygen from the air, are light-weight and are not voluminous. 
SOFC has minimizing emissions that are harmful (Like nitrogen dioxide) thus being environmental friendly. They are also fuel flexible.

Answer 2

PEM is the abbreviation which stands for Proton Exchange Membrane and SOFC is the abbreviation which stands for Solid Oxide Fuel Cell. They are a genius invention of the modern technology. PEM is light weight hydrogen cell which is not easilys catched by fire. On the other hand SOFC reduce carbon dioxide emissions and hence contribute in saving the world from the dark effect of pollution which are nowadays done in a huge scale.