That information allows them to correctly determine how much they should hold back in taxes for you, which they send to the IRS on your behalf after every paycheck.
A W-4 form (officially known as “Form W-4”) is what a full-time employee fills out for their employer when they start a new job. This form tells the employer how many deductions you will take when you file your personal tax return.
A W-2 form (officially, “Form W-2”) is provided to the “full-time” employee by the employer at the end of the year so that the employee can file their tax return.
A W-9 form (“Form W-9”), on the other hand, is filled out by a freelancer or independent contractor and then given to the company hiring them for their “independent” services.
The form you use or need depends on whether you are a company's long-term employee or a short-term contract worker hired for a specific task or service.
If you have ever been an employee, you've likely received a W-2 at the end of the year from your employer. It's not something you fill out. The form shows how much you've earned and how much was deducted for taxes and contributed to retirement plans.