What is 'selling on'?

What is 'selling on'?

Well there's a very good example of that, you know when you go in and buy a pair of shoes nine times out of ten they try to sell you the cleaning product to go with it as well. That's selling on, its suggesting something a little extra that perhaps the client hadn't thought about. For example you could say, "Well would you like me to do the planting for you", if you happen to be in landscape gardening. Or you might say, "Would you like me to quote it for maintenance", perhaps you're installing somebody website or something, its adding something extra.