When you upload an image to a page/post, WordPress automatically creates a post that contains meta information about the image. Usually that auto-generated post contains thin content, or content that has no significance for your site. This could negatively impact your SEO, as usually you need the actual media to be crawled, not the auto-generate posts. The option to redirect attachment to itself will ensure that your main media is being crawled and indexed and not the WP created URLs.
If the SEO By 10Web plugin is not installed in your WP dashboard, go to the 10Web Dashboard and enable the SEO service. In your WP dashboard, go to SEO by 10Web and click on Settings. Under the General tab, in the Defaults box, Find the Redirect Attachment URLs to the Attachment option. Choose Yes if you would like to redirect the URLs to the image itself. This will redirect the URLs to the file itself, such as jpg, ping, mp4, mp3, etc. Click Save.