Determine the direction of given parametrization.

Question

I saw an example, which I posted below.

First of all, I understand how to show paramtrized curve but I dont understand how to determine the direction of the parametrization.

For example, how can I show the direction of the parametrization

$$\tilde{c}(t)=\langle rcost, -rsint \rangle$$ for $ t \in [-2\pi , 0]$

I know this question is so easy and basic, but I dont understand enough. I am greatful if someone explains this. Thank you