A content network as it pertains to search engine marketing is the syndication network of Web content where contextual advertising is displayed.
A content network can also be defined as a network of sites that provide content (text, videos, audio, etc.) and (often) allow advertisers to show ads along side the core content.
For example, Google has it's own "approved" content network on which adsense publishers are allowed to advertise. (Advertisers must first be approved for the network based on high quality content). Many folks use an individual website (or their own group of sites) to display Google Adsense for profit. Google's paying advertisers can pay for placement on these sites, on either a cost-per click (CPC) or cost-per impression (CPM) basis.
Network Empire's Personal Brand Broadcasting (SEO Optimized) Content Network:
Students of the Network Empire method of Market Domination Web Ring Building tend to confuse (Black Hat) SEO Blog Network Linking Schemes with Owning/Building their own (Personal Brand) Broadcasting Content Network.
Much of this confusion comes from the intentional fear mongering and "marketing hype" distributed by the traditional SEO industry marketing conglomerate.
The bottom line is this; building a content network (of any size) is a legitimate and safe endeavor if you are publishing or even republishing relevant material. In fact, such an endeavor may be REQUIRED to compete and survive as a business during the ever-expanding server-based infocratic environment.
In the same way that Google views its own "content network" of approved adsense-worthy sites as a golden frame for making tons of money from Paid Advertisers . . . YOU must view your own Content Network of quality sites (both automated and curated) as a Golden Frame for your own upstream/downstream conversion and sales goals.
To Learn How To Safely Create a (Personal Brand) Content Broadcasting Network Please See Network Empire.
Note: Don't confuse a Content Network with (Black Hat) SEO Blog Network Linking Scheme