I've just read the entire thread and I'll just say that it doesn't mean a thing to me.
You could just google 'kerning'.
Fonts (yes, yes..) come in 2 general classes: Monospaced, and Proportional.
Monospaced means every character takes up the same width on the page. Like a typewriter. So I and W both occupy the same width. This has advantages, and dis-advantages. It makes tables line up nicely.
And this is one of the reasons for serifs on fonts; the little horizontal wings on the top and bottom of the 'I' glyph: to make them seem a little less out-of-place in monospaced text.
Proportional fonts vary the width of the glyphs. So I is narrower than W.
Now, kerning is how you adjust the space (and sometimes overlap) between individual glyphs. It's a visual thing. Mostly, it goes un-noticed, because typographers have done the work to make it so. But sometimes, it's done badly and is visually jarring.