[waitingforgodel]

He's using backend in the direct marketing sense... What you do with a customer after you make the initial sale (cross selling, up selling, follow up pitches, customer reactivation, referral drives, special events, etc, etc)

[il]

You got it right :) Specifically, in this case, it's all about how well you can upsell and how effectively you can email your existing customer base to keep them engaged.