Why do you need a website address?

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VKontakte when creating an application, there are fields "Site address and base domain", what are they for? In fact, if I specify the value "1" in the "Site Address" field, then nothing will change anyway, but what is the meaning of this field? What does it serve? I know that the base domain checks if the redirect matches. But what the site address is for is a mystery to me. Because it doesn't give you anything. I didn't find anything interesting in the documentation