With this iExpression you can connect a property to another one in an elastic way. This is like a linking expression, but the property follows the linked property not directly, but in a delayed, elastic way.
If you connect the position of a layer to the position of another layer, they behave as if they where connected by an elastic strap. However, you can also apply it to other properties - for example to make the scale of one layer follow the scale of another one in an elastic way.
Note that the expression only acts in one direction: The property that you apply the expression to follows the linked one but not vice versa.