No you don't, they're mutually exclusive, there are a couple of ways to check which one you're running, from lsmod to check which module is loaded on the kernel to my favorite: glxinfo | grep -i vendor

First of all don't run random commands from the internet without understanding them. Now to what that command does, glxinfo prints a lot of output about what's being used to render OpenGL, you might need to install mesa-demos, mesa-tools or something else if glxinfo is not installed by default. Then the pipe, i.e. the vertical bar | says to grab the output from the left command and feed it to the right command. grep is used to filter an input, and the -i flag tells it to do it without being case sensitive, i.e. Insensitive. Then vendor is the text you're using as a filter. Long story short that command shows information about the vendor used to render OpenGL.

If it says Nvidia you're using the proprietary driver (which you should use from your other comment). If it says Mesa you're using the open source drivers (which should be "fine" but will have very bad gaming performance)