Contentful is a pure CaaS (Content as a Service) player. It comes from Berlin, and is currently the global market leader for decoupled hosted content management.
Contentful is used by a large number of organisations from startups to large conglomerates. As a hosted solution it is a care-free option that centralises all development and hosting concerns to a single company.
Also typically to CaaS services, the customisation and integration capabilities of Contentful are limited. Pricing will also easily reach unreasonably high numbers if you have large amounts of content.