What is the spiral control used for connecting an expression to another layer called?

The spiral control used for connecting an expression to another layer is referred to as the Pick Whip. This tool provides a visual way to create expressions by "picking" a property from one layer and linking it to another. When you drag the Pick Whip from the property of one layer to the other, After Effects automatically generates the necessary expression to connect the two. This functionality not only simplifies the process of creating expressions but also makes it easier to visually manage connections between different properties and layers. The Pick Whip is widely used for streamlining complex animations and effects that require synchronized changes between multiple elements in a composition.