You submit it to USCIS to sponsor an individual for a visa.

A visa petition is the first step toward obtaining lawful permanent residence for a foreign-born individual or family. It is usually filed by a United States citizen, lawful permanent resident, or employee

By the way If you are applying for a petition based visa, your prospective employer is required to file an employment based petition on your behalf with the United States

A visa petition is the first stage in getting a lawful permanent residence for a foreign-born individual or family.