IFTTT is a service that lets other services or software (like WordPress, Facebook, Twitter, YouTube, ect.) talk to each and perform actions when certain things occur.
IFTTT literally stands for “if this then that,” and that’s a pretty good explanation of what it does.
For example, you can set up an IFTTT “recipe” (as they’re called) that goes something like this:
IF a new post is made on my WordPress blog THEN automatically tweet out a link to it on my Twitter account.