The terms networks and clusters seem to be used interchangeably in the public mind and even in some of the literature. In a business context, networks and clusters are inter-related phenomena characterised by strategies and practices of co-operation between firms.
(Source: http://www.forfas.ie/publications/forfas040624/webopt/forfas040624_innovation_networks_webopt.pdf )

Knowledge acquisition involves complex cognitive processes: perception, learning, communication, association and reasoning. The term knowledge is also used to mean the confident understanding of a subject with the ability to use it for a specific purpose if appropriate.
(source: http://en.wikipedia.org/wiki/Knowledge)

Cooperation, co-operation is the process of working or acting together, which can be accomplished by both intentional and non-intentional agents. In its simplest form it involves things working in harmony, side by side, while in its more complicated forms, it can involve something as complex as the inner workings of a human being or even the social patterns of a nation. It is the alternative to working separately in competition. Cooperation can also be accomplished by computers, which can handle shared resources simultaneously, while sharing processor time.
(source: http://en.wikipedia.org/wiki/Cooperation)