newtonian mechanics - Explanation of a Foucault pendulum

The equations of motion of a Foucault pendulum is given by:

$$\ddot{x} = 2\omega \sin\lambda \dot{y} - \frac{g}{L}x$$ $$\ddot{y} = -2\omega \sin\lambda \dot{x} - \frac{g}{L}y$$

where $\omega$ is the rotational frequency of the earth which has a value of $7.27 x 10^-5$, $\lambda$ is the latitude of where the pendulum is, $g$ is the acceleration due to gravity, $L$ is the length of the pendulum's string. What I don't know is what does $x$ and $y$ represent? I have read some derivations of these equations but I really cant figure out what they are trying to say.