Order of authorship in the original publication: Gaudelli, Komor, Rees....Liu. 

Liu and colleagues developed an advanced CRISPR system that can edit pairings of DNA nucleotide bases Adenine and Thymine into Guanine and Cytosine. In order to achieve this they created a new enzyme in the lab to chemically convert and work on the above pairings. They called this enzyme a "base editor."  In theory this tool would enable this improved CRISPR able to target a substantial fraction of SNPs (Single-nucleotide polymorphisms) associated with human genetic diseases.

(Thanks to Juan Weiss for this reference and its interpretation.)