Coined in Japan around the year 2000, "Moe" (萌えBigAT said:What exactly does this "moe" nonsense mean anyway? My character in No More Heroes 2 was screaming it over and over again and I don't have a clue why.

Or to put it another way, Moe is the ability of a character to instill in the audience an irrational desire to hug them, protect them, comfort them, help them with whatever they need/want, etc.
http://tvtropes.org/pmwiki/pmwiki.php/Main/Moe