Performing a scan allows you to detect the structure of a website, without spending time download resources such as images or archives. It also allows you to test that you have configured your crawl correctly, e.g. to exclude areas you don't want to copy, customise cookies or headers, or myriad other options.
Although this is a scan operation, it still needs to download HTML content in order to crawl it to detect other pages and resources on the target site.
Before performing a full scan, you may wish to make use of the quick scan to detect any obvious areas of a website to exclude.
It is currently not possible to pause and resume a scan.
After the scan has completed, you can use the information panels at the bottom of the window to explore the structure of the site, view errors, or information about detected files and pages.