Molecular phylogeny is the use of the structure of molecules to gain information on an organism's evolutionary relationships.
Every living organism contains DNA, RNA, and proteins. Closely related organisms generally have a high degree of agreement in the molecular structure of these substances, while the molecules of organisms distantly related usually show a pattern of dissimilarity. Conserved sequences, such as mitochondrial DNA, are expected to accumulate mutations over time, and assuming a constant rate of mutation provide a molecular clock for dating divergence. Molecular phylogeny uses such data to build a relationship tree that shows the probable evolution of various organisms.
No, C-14 dating does not come under this.