What does a USB port's 'EPR' actually mean?

There are lots of abbreviations and standards surrounding USB ports, and EPR is one of them. Here's what it means and ...
Ars Technica

Do USB extension cables reduce power?

I have a 10 foot USB extension cable on my 2.1ah 5v Apple USB charger for my iPad mini retina. Would using the extension cable have a noticeable impact on charging times or is it inconsequential? If ...