It is a way to help reach a note before beginning a song, it is also an excellent warm up tool. After warmingup your voice you can tell what parts of your range are not warmed up by humming from your lowest note to your highest, there will be gaps in which no noise comes out if you are not warmed up fully
it helps some people. It doesn't help me at all, but it does help lots of other people.
yes... that is I think one of the way to remember the note....
