Android: Netrunner is a reimplementation of the original collectible card game Netrunner. It is an asymmetrical two-player card game set in the cyberpunk Android universe, published by Fantasy Flight Games as a Living Card Game (LCG).
One player plays as a Corporation, trying to advance agendas and score them for points. While trying to score them, he must defend them from the other player, a Runner, whose objective is to steal the Corporation's agendas. The winner is the first person to score/steal 7 points worth of agendas.
The Corporation can play agendas (as well as assets that might help his game-plan) onto remote servers and defend those servers with ICE - counter-measures which can hinder the Runner's ability to access those cards - while he spends money advancing those agendas in an effort to score them. He can also play ambushes as traps, which will punish the Runner if he accesses them. The Corporation's cards are typically played face-down and can be "rezzed" (i.e. activated) and paid for at a later time.
Meanwhile, the Runner has access to resources, hardware and programs to help him steal the Corporation's agendas. In particular, he has Icebreakers which are programs that can allow the Runner to overcome certain types of ICE. As well as running on (i.e. attempting to access) the remote servers, the Runner can also run on the Corporation's central servers - overcoming ICE if necessary - and access cards from his deck, hand or discard pile. But the Runner has to be careful, encountering ICE that he cannot overcome will trigger its subroutines, which may only end the run, but could also damage him, trash his programs or have other effects.
Android: Netrunner follows Fantasy Flight's LCG model, so card distribution is fixed and there is no random element to purchasing cards. The core set has enough to build decks for any of the four Corporation and three Runner factions. "Data Packs" are expansions released each month that contain three copies each of twenty extra cards and provide new options for all seven factions, including neutral Corporation and Runner cards that can help any faction.
When building custom decks, you choose an Identity that represents a faction and can choose cards from that faction or neutral cards. You also have a limited ability to mix in out-of-faction cards as long as they fit within an "influence" budget that each Identity has. Your final deck must have at least as many cards as your Identity's minimum and no more than three copies of any specific card. Additionally, Corporations have further restrictions regarding the minimum number of points worth of agendas that must be in their deck.