What's the difference between these two?

[CNXtra]

This is just an example, the site isn't real, or at least I don't think so.

shop.yourdomain.com

yourdomain.com/shop

[sjlplat]

shop.yourdomain.com - This subdomain has a DNS entry.

yourdomain.com/shop - This is a subdirectory of a primary domain name, therefore has no DNS entry.

Both point to the same files. It's simply a fancy way to present your site.

[CNXtra]

What's a DNS entry?

[sjlplat]

DNS represents "Domain Name Server". There are DNS servers all around the world that contain the information required to display your domain name. Having a DNS entry means the information for a domain name is listed on these servers.

[CNXtra]

So... it really doesn't matter which one I use?

[sjlplat]

Not at all. It's basically just an aesthetics thing.