This is a Add to Favorites 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.
There is a "plus" sign which is like a cross, but the sides are even, centered inside a five pointed star with all sides that are equal. Both are outlined in black. The star is "hollow" otherwise" in that there is empty space surrounding the icon. Everything is straight (there are no curved lines).