First thing - The links displayed below the description are not sub-links but site-links. Secondly, it shows that these are the quality and unique pages on the site. To find if the site is authentic then: 1) Check the About Us page. 2) Check the Contact Us page. It must have authentic physical address. 3) Check the privacy policy page. 4) Check the domain age and see who is the owner of the site 5) See the PR of the site. 6) Check the backlinks of the website. If anyone knows something more, please share
If Google shows the site-links below the description mean that site was very useful and relevant to the visitors for the particular keyword.