It's a logo of an equilateral triangle. Slightly tucked behind it on the right side is another equilateral triangle of slightly smaller size.
This is a Pyramids 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 13,700 icons, all in the same style and quality.