This About icon is a responsive icon. This means that it's optimized for four resolutions, from tiny 16x16 until highly detailed 80x80. The style comes from the latest Microsoft Office, which makes it perfect for any Windows applications, in particular, those with ribbon toolbar control. Unlike other icon packs that have merely hundreds of icons, this monster icon pack contains 15,500 icons, all in the same style and quality.
It is a speech bubble with the letter "i" in the center. The bubble is not an exact circle, but rather a horizontal oval. The letter "i" is lower case, and one would think that by seeing this icon you would be informed about a certain topic presented with it.