Rendering is the process where we composite our After Effects project or work into a final video or an Image.
Once you are done with your project, you can render out your video by going into Composition > Add to render queue or use the Keyboard shortcut key Ctrl + SHIFT + /. To render out an Image, Go to Composition > Save Frame as > File.
When your project is added to the render queue, setup your Output module. In that you have to setup the format of your final result along with the frame sizes, audio settings etc. Under Output to, you can setup the destination location where you want your final result to be saved.