What's the difference between a stud finder and an electronic stud finder?

A manual stud finder (the knock test kind) relies on you tapping the wall and listening for a solid sound, which takes practice and honestly isn't super reliable. An electronic one uses sensors to detect the density changes behind drywall, giving you a beep or light when it finds a stud - way faster and more accurate, though you do need to replace batteries sometimes. If you're hanging heavy stuff, the electronic version saves you from drilling holes in the wrong spots, which beats the old-school method by miles.

The knock test isn't really a separate category from electronic ones - it's more like the ancient predecessor that most people abandon pretty quickly. When I hung some shelves last year, I tried the old tapping method first and spent twenty minutes convinced I'd found studs that turned out to be just hollow spots between them. Switched to an electronic finder and located them in seconds. The sensors (usually magnetic or motion-based) do the heavy lifting, so unless you've got genuinely perfect hearing and a lot of patience, you're better off with the electronic version - are you dealing with a particular wall thickness or material that's giving you trouble?