Question: URLs and URNs are subsets of URIs.

There are many answers on Stack Overflow that explain the concepts quite nicely. You often find a Venn diagram where URNs and URLs are overlapping sets, implying that each of the three areas are not empty. I can imagine a URN that's not a URL: the ISBN of a book. I can also imagine a URN that's also a URL: a normal web address.

What would be examples of URLs that are not URNs?

Answer: 
According to the [classical view](https://www.w3.org/TR/2001/NOTE-uri-clarification-20010921/#classical), a URI can either be a URL or a URN (or possibly something else), not both:

> 
> During the early years of discussion of web identifiers (early to mid 90s), people assumed that an identifer type would be **cast into one of two** (or possibly more) classes. An identifier might specify the location of a resource (a URL) **or** its name (a URN) independent of location. Thus a URI was **either a URL or a URN**.
> 
> 
> 

So in that view, any URI that specifies the resource’s location would be a URL, and never be a URN in addition.

(According to the [contemporary view](https://www.w3.org/TR/2001/NOTE-uri-clarification-20010921/#contemporary), this distinction isn’t considered to be useful. [It’s recommended](https://stackoverflow.com/a/42546900/1591669) to use the term *URI* or *URL* for all cases.)
* URI : Uniform Resource Identifier
* URL : Uniform Resource Locator
* URN : Uniform Resource Name

A URI identifies a resource, it is done either by location (URL) or by name (URN).

See: [URI on Wikipedia](https://en.wikipedia.org/wiki/Uniform_Resource_Identifier#Relationship_between_URIs.2C_URLs.2C_and_URNs)

EDIT
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A URL like `http://example.com/` does not name the resource, just the location it could be get. A resource naming URL would be `http://example.com/index.html`...