This is a Info Popup icon. We've made it in iOS style, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 12,500 icons, all in the same style and quality.
This icon for info popup is depicted as a square. At the bottom of the square in its center there is a small protrusion outward ending in a sharp point. At the top of the square is a line running horizontal across it. In the center of the square is a large lower case letter i.