Known as pysanky—from pysaty (писати), "to write"—in Ukraine and as
pisanki in Poland, they are eggs decorated using the wax-resist method
(resist dyeing). The words pisanki/pysanky are sometimes used to
describe any type of decorated egg, but they traditionally referred to
an egg created by the wax batik method and utilizing traditional folk
motifs and designs. The designs are "written" in hot wax. While the wax
resist eggs of the various Slavic nationalities may appear somewhat
similar, they can be differentiated by color schemes, divisions used,
and motifs.
📖Read on Wikipedia