Yes it does work (or at least it can). What you basically do is make a parabolic antenna that reflects the WiFi signal. You need to aim it in the direction of your laptop/tablet/PS4/etc, so it won't necessarily help in every case of poor signal strength. Where I personally used a tin foil with some success was while staying at a long, single story house with the wireless router at the opposite end from my bedroom.
Here's a link to a video on how to make a tin foil booster. I've never made one out of cans because, honestly, I'd probably cut myself. All you really have to do is make a 8-10" tall sort of "C" shape out of tin foil and place it on its side behind your AP's antenna, with the open end of the "C" pointing in the direction of the wireless device that you want to have a stronger signal. Don't expect miracles, but it can make a moderate difference.