Helicase is an enzyme that unravels DNA when it (DNA) is being copied for a new cell.
DNA (Deoxyribonucleic Acid) is the molecule inside cells that contains the genetic information responsible for the development and function of a living thing.
Helicase unraveling DNA is a part of a greater sequence of steps called DNA Replication in Biology. DNA Replication is the sequence of steps that DNA undergoes to be copied into a newly forming cell since DNA is usually bundled up into bundles of DNA called Chromosomes.
Without Helicase, we would quite literally not be able to grow.