Add one CH3 group and you get 4-methylresorcinol. It sounds like a tiny change. Chemically, it isn't. The methyl group breaks the symmetry of the original molecule and changes the electronic and steric environment around the aromatic ring.
Now the remaining carbon positions are no longer equivalent. Chemists can exploit those differences when deciding where to build the molecule next. But there's an even more interesting story. Enzymes notice the difference too.
Global Chemical Database