The Basics 
Move tool is used for moving anything on the image, including layers, selections and paths.
- Move - defines what will be moved
- Tool Toggle - toggle between the two available modes (for each option)
You can toggle between the two options with Shift (temporarily).
You can choose what you want to move, as mentioned before it's either layer, selection or path.
To move a layer, select this option. If the layers are grouped (chain symbol), all layers in the group will be moved.
When this mode is selected, under tool toggle you'll see two options, "Pick a layer or guide" and "Move the active layer". The first one will move the layer that you select and the second one will always move the active layer.
The move tool allows you to move the selection outline. It has no options in Tool Toggle.
You can also move paths with this tool. Note that path tool has its own tool for moving. To use move tool, make the path visible in the path dialogue.