I\'m trying to find useful tutorials about how to create modern websites that loads content without refreshing the page.
I have tried all kinds of words in Google, but I
tl;dr:
Googling ajax website tutorial or jquery address tutorial is a good start.
As has been noted, the key here is AJAX.
AJAX alone, however, is not the answer. It's pivotal to a non-page-reload site, but there are also a lot of other things to consider.
Luckily for us all, the Internet is great, and lots of developers have an open-source is awesome mindset.
Suffice to say, this type of site has been done before, and there are people out there who have made developing a site like this easier.
Ignoring the back-end & server-side setup, the way I would recommend starting a site like this is to use the following:
Use the plugin from the start; from experience, it's difficult to implement it after you've completed the site.
You'll want use ajax. There are also ways to poll the server for updates as well. You can use a setInterval call to periodically retrieve a URL; but this is only required if you're polling. If you're doing this action based on a user event, you can just use that to trigger the retrieval/update. I'd suggest looking at jQuery, it'll make this kind stuff much easier.
jQuery Ajax would make it possible in a simpler way!
There are frameworks built exactly for this. One of today's hot ones is Meteor.js.
Read about it. Worst case, you'll get your googling keywords and find an alternative you like.