The digital era or more aptly, the "4th IR" has brought with it, new and in some cases repackaged old things in new "wine-skins." A more intriguing development, is the new vocabulary that the advent of digital spawned. You hear words such as, like, follow, tweet, inbox me etc.,

Equally, one hears of most new start up businesses in the digital era as either networks, marketplaces, platforms or any of the three (3) combinations.

What exactly are "networks, marketplaces and platforms?" Are there any differences between the three (3)? Please give examples to bring your response to life.

Thank you in advance.