After pilot programs in international markets like Japan, Singapore, the United Kingdom and Brazil, FedEx will deploy a fleet of electric delivery vans in Washington DC. The goal is to test the Nissan e-NV200, which is 100% electric, under real-world conditions and, we can assume, eventually use EVs on a large scale and burn less fossil fuels to get packages to you.
The electric e-NV200 is based on the LEAF platform, so it shares a lot of the same components. This means that if the e-NV200 is adopted by large fleets (not only FedEx, but maybe UPS, the postal service, taxi fleets, whatever), this will help drive down the cost of 'civilian' EV through economies of scale. Not a bad deal.
If the e-NV200 looks familiar, it might be because you saw the non-electric version that was picked to be New York City's "taxi of tomorrow".