1) Criteo is an advertising technology company that uses machine learning to target personalized ads to users across devices.
2) It has over 2000 employees, works with 16,000 publishers and 11,000 advertisers worldwide, and generated $11 billion for its clients in 2015.
3) Criteo's machine learning challenges include selecting the best products and ads to show users from huge catalogs in milliseconds, building a graph connecting billions of devices to identify users, and extensively testing new models and systems.