How To Determine Which Lightroom Catalog You Have Open
In my teaching, and spending time in the Adobe forums I see people struggling with this. They open Lightroom and all the work done on a previous day has some how been lost, and they are certain Lightroom is at fault. Of course Lightroom is not at fault. They've simply opened a different catalog than the one previously worked in.
I recorded this video to explain how to figure out what catalog you have open.