You can render from a command line if you want to render an animation or single frame. Advantages include the following:

• works with single images and animation
• uses less memory than having all of Maya (UI) running
• can be scripted
• can be integrated into a rendering pipeline (render farms)
• for Maya software rendering, you can override render settings using command flags (for other renderers, you must also write a MEL script)

For more information, see Command line renderer in the Rendering Utilities guide.