Objective
Players of the game belong to one of two factions, “Enlightened” (represented in green) and “Resistance” (blue). The game-play allows players to enclose regions of territory on the surface of the earth with virtual links between virtual portals, which are visible in the game software. The top-level goal of the game is for one’s faction to control large numbers of “Mind Units”, the estimated number of humans within the regions of territory controlled by the faction.


A player using the mobile app is presented with a map representing the area nearby. The map has a black background; streets and buildings are represented in grey, but not named. Visible on the map are portals, Exotic Matter, links, and control fields.
To interact with objects on the map, a player must be physically nearby their location. The mobile client represents the player as a small triangle, surrounded by a circle which represents the perimeter within which interaction is possible.

Detailed Description: http://ingresswiki.org/wiki/Main_Page

Main Page: http://www.ingress.com/

Also, a great place to try to get your hands on a beta key and get started:
http://www.reddit.com/r/Ingress
http://www.reddit.com/r/IngressInvites