What exactly can I do with a CCNA Discovery 1 certification?

This sounds like a Certificate of Course Completion - the actual CCNA is not broken down into Exploration and Discovery paths. What is more, it sounds like it is only the first module - the full CCNA curriculum is spread over four modules. As such you don't really have a substantive qualification at all there but a certificte saying you did part of a course to get one. CCNA is a lot of work and you'd know it if you had studied for the complete qualification.