It is a light bulb. Inside of it, there is a “Y” sort of drawing to indicate the inner workings of the bulb. It also has the screwing part on the bottom of the bulb.
This Idea icon is made in Material Design style
developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 5,700 icons, all in the same style and quality.