What is e-rupee and why do Google Pay, PhonePe want to join RBI’s digital rupee project?

Google Pay, Amazon Pay, and PhonePe are looking to join the RBI’s digital rupee pilot project. What exactly is the e-rupee, how is it different from banknotes, and what was the need for it?

​Google Pay, Amazon Pay, and PhonePe are looking to join the RBI’s digital rupee pilot project. What exactly is the e-rupee, how is it different from banknotes, and what was the need for it?