A checkpoint is when the system syncs all the information in the transaction log into the MDF/NDF files, so that the log can be truncated. It uses a queuing mechanism to do this, saying "When you have a moment, do this..."
Presumably you don't actually mean that you're looking for b.name = '', but more like, a specific database. If the checkpoint is the only thing you're seeing there, then it means no-one is connected to the system, and the only thing going on is making sure that the transaction log is empty.