'The transfer (or outsourcing) of part of an undertaking to a third party for better service or lower cost from a specialist in that niche'. Other benefits can include the release and refocusing of business resources to new areas of where more profits can be earned'.
Transferring part of your business to a third party who is going to run it for less, or provide a better service. Two choices here: a) It's for companies that cannot run part of their operation so they outsource it in frustration, or b) It's a great way of bringing niche expertise to tackle a non-core part of your business so that you concentrate on bigger and more profitable things.