Two-factor authentication, also called multiple-factor or multiple-step verification, is an authentication method to double-check that your identity is legitimate.
2FA will offer you an extra layer of protection, besides passwords. It's hard for hackers to get the second authentication factor, they would have to be much closer to you as its always related to a physical device, such as a token, mobile phone, SIM, USB stick, key fob, ID card, etc. This reduces their chances to succeed greatly.
Emails inboxes on their own are vulnerable to cyber attackers. If you're receiving sensitive information to your inbox while unprotected, this could give them further access to other websites such as your YallaBit account.