A redirect URL is used in OAuth 2.0 to redirect users to an application after they grant permission to access their account. Specifically, this URL is used in the authorization code flow with PKCE, which is an enhanced security method to prevent authorization code interception attacks.

In this flow, two URLs are required: the authorization URL, where you request permissions and provide additional authorization information, and the redirect URL, which points to your OAuth application and receives the authorization response. When the user grants permission, the authorization server sends an authorization code to the redirect URL, which the application can then use to obtain an access token and refresh token.

It's important to note that the redirect URL must be registered with the OAuth provider and must match exactly to prevent attacks. Let's say your OAuth application is called "MyApp" and you want to redirect the user to a page on your website called "https://www.myapp.com/auth". You would set the redirect URL to "https://www.myapp.com/auth" when you register your OAuth application with Teya. When the user clicks the "Authorize" button, they will be redirected to the authorization URL on Teya's server. If the user grants your OAuth application access to their account, Teya will redirect them back to your redirect URL, "https://www.myapp.com/auth", along with an authorization code that your application can use to obtain an access token.

You can read more about it here.