They get resized at the same time. The selection is also not lost when you resize a layer , but in this case the selection does not get resized with the layer. Black areas are not selected, white areas are fully selected. Masks can be be into selections using the Mask to Selection option of the Layers menu. Option clicking the Eye icon of a layer hides all the other layers.
Arrow keys can move selections by one pixel at at a time.
Shift-Arrow key moves them by 10 pixels at a time. The Alt key must be pressed first before using the arrow keys to move the selection. Shift-Alt moves it in larger increments. Arrow keys can be used to move layers up and down the layer stack. If a layer is selected, its mask appears in the Channels palette, enabling you to use it without having to switch between Layers and Channels.