Rocket buys inventory on online ad exchanges (e.g. Google's DoubleClick, Yahoo's Right Media), uses artificial intelligence-based algorithms and mountains of data - the S-1 has plenty of references to that beloved buzzphrase, "big data" - to predict how users within one of its 20K+ "unique audience segments" will respond to a particular ad, and then uses its findings to target and deliver ads provided by advertiser/agency partners.
2/3 of Rocket's revenue is tied to ads meant to yield a particular response, such as a click or a purchase, and the rest is tied to brand ads. Tailored solutions are offered for display, video, mobile, and social media ads.
The company had 1H revenue of $92.6M (+134% Y/Y), and a net loss of $11.9M. Opex rose 162% to $51.7M, with 67% of it going to sales/marketing spend. 2012 revenue was $106.6M (+138%), and net loss was $10.3M.