With either side of a connected layer selected, the Layer Inspector will show Connected Layer Properties.

The default behavior is for whichever layer is lower in the layer list, to be moved up to match the position of the higher layer. Then, the incoming layer's properties such as position and size are matched to the outgoing screen's layer. The layer animate together to the end state which is defined by the outgoing screen's layer. The incoming layer will fade in on top of the outgoing layer.

You can modify this behavior using the options in the Connected Layer Properties.