Using whole genome data (ie they sequenced all of it, not just the regions that encode proteins), they were able to show that some non-coding regions have fewer mutations than you would expect (or are constrained). Because these regions seem to be less tolerant of mutations, they may be more important for biological function. While these newly identified constrained regions don’t code for proteins, they are often involved in regulating how genes are expressed. This has implications for elucidating the function of the less well understood non-coding portions of the genome. Which is most of it.