This is an important question, as many people are confused as to what Ingress or Niantic Project even are. The short answer, is they are all apart of an Augmented Reality Game (ARG) that is the output of a division of Google, Inc. called Niantic Labs. Ingress is the name of the game and application hosted on the Google Play Market. The Niantic Project is a top secret project commissioned by the National Intelligence Agency (NIA).
There has been quite a bit of publicity surrounding the game, starting as early as Comicon 2012 in San Diego with a secretive comic artist specialist, Tycho. There was a great amount of a buzz regarding Tycho and posters that he had made that were inspired somewhat by premonitions? Regardless, people wanted to find him, no one knew who he was, and he appeared during a key note presentation having to be escorted out of the room due to his erratic behavior.
P.A. Chapeau (PAC) has been a key player in the investigation of the Niantic Project. He is the one who has setup the Investigation Board that provides us a picture of what the Niantic Project is all about, by displaying leaked documents, strange events, and other media.
I could write more, but here is a great video that summarizes the first few weeks of information which I think is worth reviewing.