Primase is an enzyme that creates primers, which are short RNA sequences which are complementary oligonucleotides linked to a nucleic acid polymer.
The primers are used to start the DNA synthesis process.
A primase is a form of RNA polymerase since it creates RNA molecules.
Primase is essential because DNA polymerases can only extend from the 3′-hydroxyl of a primer and cannot commence polymer synthesis on single-stranded DNA templates.