Since one of the main goals of this bootcamp is for you to build a website, it makes sense that it's a good idea to have a good grasp on what exactly is a website beforehand, from a more technical level.
Websites are something you interact with quite often; you're interacting with one right now, and thankfully as an end user, you don't have to care much to how they work, but if you intend on making websites, it helps to build a better view of how they work.
What is a URL exactly?
URL, which stands for Uniform Resource Locators, is an 'address of a given unique resource on the web'.
MDN explains this quite well here.
...A URL is nothing more than the address of a given unique resource on the Web. In theory, each valid URL points to a unique resource. Such resources can be an HTML page, a CSS document, an image, etc. In practice, there are some exceptions, the most common being a URL pointing to a resource that no longer exists or that has moved. As the resource represented by the URL and the URL itself are handled by the Web server, it is up to the owner of the web server to carefully manage that resource and its associated URL.
To use an example, lets talk about the very website you are on.
Here, we are using the scheme 'https', we are on the subdomain 'hackfrostnl' of the domain 'github.io' (which itself has a top level domain of 'io'), on the path '/'
In this circumstance, we are on the same exact scheme / subdomain / domain, but our path is different, it is now '/dev-bootcamp-v1.0/web/overview.html', hence you are viewing this section, and not a different one.