This is a speech bubble. The speech bubble is in the shape of a rectangle with rounded edges and a little comma on the bottom left that would point towards the speaker. Inside of the speech bubble are 3 circles in a horizontal line.
This is a SMS 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 13,300 icons, all in the same style and quality.