A project is a group of spiders that are normally closely related and mostly crawl sites or data in the same category or industry. Therefore, you can regard projects as a method of grouping spiders together so that they could be better managed.
It is in one-to-many relationship with spiders.
You can link a spider to a project by either,
Projectin the spider detail page, or
Projectin the create new spider dialog.
Spiders tab in the project detail page.