How to create a content type to embed video in drupal 6?
You are looking for Embedded Media Field module. After enabling just paste the URL of the video, it will render the video on the page. It supports almost all the videos like youtube, vimeo, etc.. 


  This extensible module will create fields for content types that can
  be used to display video, image, and audio files from various third
  party providers. When entering the content, the user will simply paste
  the URL or embed code from the third party, and the module will
  automatically determine which content provider is being used. When
  displaying the content, the proper embedding format will be used.