The feeling of comfort, sort of like the feeling one gets from a warm, soft blanket; usually a feeling one gets when one embraces the familiar. The opposite, in many ways, of FearUncertaintyAndDoubt.
Frequently used by marketeers--in the absence of objective data (or even in its presence!) to demonstrate the superiority of their solution/product, try to make that which is being sold seem familiar, comfortable, and coming with minimal risk. Wouldn't you really rather buy IBM? The companion technique--again--of FearUncertaintyAndDoubt.
The term "WarmFuzzyFeeling" often has a derisive meaning--implying that the perceived advantages of something (the "warm fuzzies") are superficial, and that the person perceiving the WarmFuzzyFeeling is reacting based on emotion and/or instinct, rather than doing a careful analysis of the situation.
Term also refers to emotions one feels upon doing something that someone believes to be a good thing. (Or a bad thing that one enjoys; CatBert? is known for getting warm fuzzies from implementing obnoxious HR policies that further afflict the poor employee's at Dilbert's corporation).