An employment contract regulates what work you do as an employee (the person who works) for the employer. It is a contract between you (employee) and your boss (employer).
In the employment contract it says what work you do and how much money you get for it. The employment contract can be concluded in writing (the employee and employer sign it), verbally (meeting/phone call in person) or electronically (via WhatsApp/e-mail).
After one month, your employer must provide you with written proof!
When you get an employment contract, you don't have to sign it straight away! You can read through it first in your own time, or take it home with you. Don't let anyone force you to sign the contract immediately!
If there is anything in it that you don't understand, get help from your advice centre.
Note: you should always ask for a written contract. If problems arise later, verbal agreements are difficult to prove.