
IFTTT stands for If This Then That and it works just like that. If you post a picture with Instagram, you can have it post to Flickr at the same time without doing anything extra. Within IFTTT, you create a "recipe" for whenever you post in Instagram, also post to Flickr. Same goes for if you post to Twitter, have it also post to Facebook. If you bookmark a webpage, you can have it post to Evernote too. There are lots of different social websites to choose from and you can create your own recipes.
What's more is that you can look in the gallery and find "recipes" that others have created and use those! My first recipe was to post to Twitter any website that I bookmark to Delicious. And so it begins...