Native advertising is a form of online advertising that matches the form and function of the platform on which it appears. The word "native" refers to the content's coherence with other media on the platform.
One form of native advertising, publisher-produced brand content, is similar in concept to a traditional advertorial, which is a paid placement attempting to look like an article. 
Formats for native advertising include promoted videos, images, articles, commentary, music and other media. Examples of the technique include Search advertising (ads appearing alongside search results are native to the search experience) and Twitter with promoted Tweets, trends and people. Other examples include Facebook's promoted stories or Tumblr's promoted posts. Content marketing is another form of native advertising, placing sponsor-funded content alongside editorial content  or showing "other content you might be interested in" which is sponsored by a marketer alongside editorial recommendations.
The types of platforms and websites that participate in native advertising can be split into two categories, “open” and “closed” platforms:
Closed platforms are brands creating profiles and/or content within a platform, then promoting that content within the confines of that same closed platform. Examples include Promoted Tweets on Twitter, Sponsored Stories on Facebook, City, Vivas and TrueView Video Ads on YouTube. Large publishers, such as Washington Post, have recently started introducing their own native advertising formats.
Open platforms are defined by promoting the same piece of branded content across multiple platforms within native ad formats. Unlike closed platforms, the branded content asset lives outside the platform.
Hybrid platforms allow publishers to install a private marketplace, while having the option to allow advertisers from other platforms to bid on the same inventory either through direct sales or programmatically through Real-Time Bidding (RTB).