User-journey tests are a form of BusinessFacingTest, designed to simulate a typical user's "journey" through the system. Such a test will typically cover a user's entire interaction the system in order to achieve some goal. They act as one path in a use case.
They are usually BroadStackTests and as such, are usually slow to execute and prone to being brittle. Consequently suites of user journey tests usually aren't built to be comprehensive tests of a system's behavior. Usually you will have only a few user journey tests to exercise the integration of the system as a whole - probably only one path for each use case (usually the happy path). Verification of all the variations in behavior is left to tests done in different styles, usually with more focused coverage.
In contrast to StoryTests, user journey tests are not tied to user stories. When you play a story you look at the existing user journey tests and modify them to support any change in behavior implied by the user story, only rarely does a user story lead to an entirely new user journey test.