A known problem is that of search engines simply ignore pagers. When indexing a site, they only use the information contained within the first page. The reason for this is that pager links are usually not represented as hyperlinks to other pages. Instead, they simply respond to click events to raise data update callbacks.
If this property is set to CrawlerOnly, hyperlinks are rendered in the pager when a web-crawler is detected. For other visitors, standard pager links are generated. So, search engines can index the entire content, while site visitors experience the same callback functionality.
If the property is set to Enabled or Disabled, automatic web crawler detection is disabled. The pager renders either SEO-friendly or standard links respectively.