why is there an e where my 4g should be?

why is there an e where my 4g should be?
'The E stands for EDGE (Enhanced Data rates for GSM Evolution) can reach speeds between 120Kbps to 384Kbps. This was the original iPhone's top data network speed. Now it's met with a sigh because it means where you're standing doesn't have a 3G or 4G signal. '
Full answer in: www.marieclaire.co.uk