Fic recommendations, commonly known as recs, are a common practice in fandoms that have become too large to easily search for goodfic through the various fanfiction archives online.
They are commonly organized in lists by one or more person, or in large communities dedicated to linking stories that others think should be shared. These lists or communities are often grouped by theme, genre, fandom, and occasionally by 'ship. Alternatively, they are linked directly to you by someone who found the fic too good not to share.
Some people in fandom, once they have become tired of trawling through archives themselves to find goodfic, finding only badfic or worse eventually give up and depend entirely only on recs, finding solace in someone else having done all the hard work for them already.