When you click on troops and tell them to go somewhere, by preessing the x key they will immediatly stop.
This is a very useful keybind, it creates a rally point. The rally point is something that will tell any troop that has been created after the rally point to go to the rally point. Even if the rally point is on land it will still tell water vehicles to go to the nearest water tile to that point.
This key isn't too complicated however it is a weird key to use. The z key cancels everything. So if you are in a menu for the training camp and press z it will exit the menu. Or if you selected a unit it will cancel out of that unit.
B standing for building, obviously is the key you use to build. By pressing this key it pops open a building menu with all the buildings you can buy and how much they cost. By clicking one you can then drag it to the game and place it where you want it.
This key brings up a little menu where you can sea a boat and a helmet. The boat represents your navy and when you hold left click until the whole section turns blue, you have now selected every naval unit. On the other side when you hover over the helment and let go you have now selected every ground unit.
When selecting buildings that can create units, you can use the number 1-6(Depending on the building) in order to select which unit to make.
-Credit to NoobyandApple-