How to determine what command is being run, and "reveal" where that mapping is defined?

[macintacos]

I have a mapping that is defined somewhere in which-key. I know the key combination that makes it do what I want it to do (for example, <leader>fe). Let's assume that it is defined explicitly by which-key somewhere, and I don't know where (meaning - which-key is being used to define it, it's not something that which-key "picks up" based on already-existing mappings). How do I figure out:

• Where is this mapping defined?
• What command is that mapping running?

Searched around and couldn't find this answer, apologies if this is already called out somewhere.