There are many classic tech debates, and the question of what to formally call web addresses is one of the most nuanced. The way this normally manifests is someone asks for the "URL" to put into his or her browser, and someone perks up with,

Actually, that's called a URI, not a URL...

The response to this correction can range from quietly thinking this person needs to get out more, to agreeing indifferently via shoulder shrug, to removing the safety clasp on a Katana. This page hopes to serve as a simple, one page summary for navigating the subtleties of this debate.