This Enter 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 4,600 icons, all in the same style and quality.
An enter icon is a rectangle shape and between one of the sides of the rectangle there is an arrow. The arrow is going through or entering into one of the sides of the rectangle, which shows something is entering.