What is the difference between Turn Coordinator and Artificial Horizon?
Attitude Indicator
It shows your attitude (nose up / down, bank left / right) relative to a horizontal surface. Basically, it tells you the orientation of the plane if someone were to take a photo of the plane from the outside at this very moment.
It does not tell you which way you are going (e.g. you can be nose up but descending).
Turn coordinator
This is actually two instruments in one: the white plane and the little ball.
The white plane tells you which way you are yawing (rotation about the normal (vertical) axis)). If you are yawing to the right (e.g. N -&gt; NE -&gt; E), the right wing of the little plane is lower. If you are yawing to the left (e.g. N -&gt; NW -&gt; W), the left wing is lower.
If you are yawing at the standard rate (3 degrees per second), the wing of the little plane will align with the white mark.
Combining the two
Suppose that you manage to yaw the plane to the right while keeping it horizontal, like a spinning top:

You will get: