How do you turn off two factor authentication

2 Step Verification or 2 Factor Authentication?

2 Step Verification 

How do I turn off two-step verification?

Sign in to your Apple ID account page.     

In the Security section, Click Edit.

Click Turn Off two-step verification.

Create new security questions and verify your date of birth.

You'll get an email confirming that two-step verification for your Apple ID is off.

Apple ID - Two Step Verifications FAQ.  *

2 Factor Authentication 

From the article below. 

Can I turn off two-factor authentication after I’ve turned it on?

If you already use two-factor authentication, you can no longer turn it off. Certain features in the latest versions of iOS and macOS require this extra level of security, which is designed to protect your information. If you recently updated your account, however, you can unenroll for a period of two weeks. Just open your enrollment confirmation email and click the link to return to your previous security settings. Keep in mind, this makes your account less secure and means that you can't use features that require a higher level of security.

Apple ID -Two-factor authentication.   *

You’re not going to be able to do so.

What problems are you having which make you desire to disable Two-Factor Authentication (2FA)?

Some info on how it works:

Two-factor authentication for Apple ID - Apple Support

and

Get a verification code and sign in with two-factor authentication - Apple Support