Being designed to work with TVs, you may find that your Pi is only using the middle portion of the screen and there is a big unused area all round the screen.
This is not true of all TVs and monitors, but if it's happening for you then selecting the option to Disable Overscan may fix this for you.
Use the left and right cursor keys to make your selection and then hit Return.
Last updated on Feb 27, 2018
Published on Dec 04, 2012
If after disabling overscan, you cannot see the left edge of the screen then see the section 'Running Raspi_Config After Booting'.