-The right paddle shifts the rear derailleur into higher gears.
-The left paddle shifts the rear derailleur into lower gears.
-You press both paddles at the same time to shift the front derailleur.
-You can swap batteries between the front and rear derailleur in case you forget to charge them. The derailleur will stay in the gear it was last in when the battery dies or is removed.
-The wireless technology it uses was created specifically for SRAM eTap. It relays signals instantly and can send multiple signals at once. Being able to send multiple signals at once means you can shift the front derailleur while shifting the rear.
Why does it even matter? The mechanical Red is lighter and less expensive. But it's not as cool. The benefit of electronic shifting is that your shifting is consistent, accurate, and extremely quick. The benefit of wireless is that it works well with any bike you add it to. Being a bike mechanic, this is a big deal to me. I've had numerous issues trying to get electronic cables and junction boxes to fit where they weren't meant to. Keeping cables in a good position on frames with external routing can look unsightly. Very few people are going to be adding eTap to a bike that has external routing, unless that frame is a gorgeous, lugged steel or titanium frame.
eTap is available now. It's in stock at The Bike Shoppe. Its cool. And should I stumble upon a large sum of money that takes care of my financial woes, it will be on my bike. Or I'll put it on a credit card and have Future Me take care of Present Me and pick up the bill when it comes due. It may help me ride Salt to Saint as a solo entrant. There's my justification, I must have it now.