URLs are the addresses of the internet. Each URL points to a location and your user can go there. However on the internet the addresses are not that important to the users and browsers. Especially since we can read almost any page on such a location. So the location doesn't matter as long as we find what we expect.
The URL and the link text both build an expectation in us. The text and the URL will imply what we will find after we click the link. I think it makes sense to write links without showing the URL.
For example when I wrote some code and pushed it to GitHub, I could write it like this:
I posted my new code to GitHub: http://github.com/pstuifzand/pompiedom-river.
Or I could write:
I just released a new of version of Pompiedom, an rssCloud-enabled realtime river.
The second example explains what you will find when you click the link. Another reason for writing text instead of URLs is that the layout engine has more to work with when breaking lines, especially when using justified text.