Even though we move more towards streaming and digital media, many people still have movies, music and games lying around at home on physical media such as CD and DVD. If you want to burn a Blu-ray movie or put your holiday pictures on a CD, you need to have a drive in your computer.
Many new laptops have also become so thin that there is no longer room for a DVD or Blu-ray drive. If you want to watch a movie or listen to music, you will need to buy an external optical drive. For a desktop computer, you need to buy an internal drive and for a laptop computer, you ned to choose an external drive. The external drive is connected via USB, where an internal drive fits into a 5.25" drive bay.