The next official release of LW will only ask you once when starting up whether you want LW to be the magnet handler. This is already avaliable in the LW 4.13 beta.

At present (LW 4.12 & earlier), if LW detects it is not the magnet handler it will ask you about it each time it starts. The way to find out what is your magnet handler is to download a magnet link. Unless you have 2 LW versions installed.

As OAH suggests clipboard is simply a portion of memory put aside for when copying things such as text or images. On my mac, i have a program called Butler which allows me to see the clipboard & also gives me the option of having more than one clipboard & saving the clipboard between reboots. I just checked & it has 9 pasteboard recordings at present despite I haven't used the clipboard since booting up less than an hr ago.