Crawl Order controls how the crawl determines what to crawl next.
Breadth-first Search means that Yioop first crawls the seeds sites, followed by those
sites directly linked to the seed site, followed by those directly linked to sites directly linked
to seed sites, etc.
Page Importance gives each seed site an initial amount of cash. Yioop then crawls the seed sites. A given crawled page has its cash splits amongst the sites that it link to based on the link quality and whether it has been crawled yet. The sites with the most cash are crawled next and this process is continued.