The tagline for IFTTT is Put the internet to work for you. What then mean is that you can automate tasks, allowing for you to create workflows that you didn’t believe were possible or were too time consuming. IFTTT is short for If This Then That. To begin using IFTTT, you add channels for services that you use, such as Twitter and Evernote. Once the channels are added, the magic begins with the creation of a recipe.
A recipe consists of a trigger (This) and an action (That). For example, a recipe may be that whenever I favorite a tweet, append the tweet to a note in Evernote. I would then have a note that contains every tweet I favorited (after the creation of the recipe, of course :-).
The idea seems simple on the surface, but then adds depth and capability the farther down the rabbit hole you go.