EMotion FX is a full animation system. It is used in games to animate characters and customize characters, etc. Basically it tells you the positions and rotations of the bones in your character or of your robot, based on the animations you play and how you blend them together etc. So if you have say a game and you want to add animated characters to it, like a character you can control with a game controller, then EMotion FX is a good choice. So here you tell like: if i press this button on the game controller, play an animation that makes the character jump.
IKinema is an Inverse Kinematics solver. You tell where you want the hands of your character (or robot) to be, and it will calculate the pose of the bones. So if you try to modify an existing pose or try to make the robot reach for something, then this is what IKinema does. So it works the other way around (hence the Inverse). It does not really animate your character, but allows you to adjust and correct poses so that given bones reach given positions or rotations.
EMotion FX also has Inverse Kinematics solvers inside, but they are not as good as IKinema as IKinema is really completely specialized in that.
Generally speaking, if you want to tell your robot what to do, IKinema would be something that would be more interesting for you. As you will specify exactly where you want to have the legs etc. IKinema can nicely calculate the pose of your robot required in order to reach that goal. Unfortunately it will most likely be a bit more complex than that, as you have to probably do it physically in a way so that the robot doesn't fall over and lose its balance too. In games we don't really have that problem unless we run a full physics simulation to make a character walk, which would make it similar to making a real robot walk :)
Hope that helps a bit.