When I want to configure an addon, for example Ghostery, the tab shows a URL like this one:
What does it mean? Does it have something to do with the Chrome browser?
chrome has been used by Mozilla since long before Google Chrome came on the market. Typically the phrase "Chrome" referred to all the area around your viewport, but not the viewport itself. Sort of like the chrome plating some cars have around their windscreens or headlights.
See here for more details - but no; nothing to do with Google Chrome.
This is a type of binding in firefox that has existed for some time. Chrome refers to the user interface of the browser. For instance this includes everything outside of the webpage you're viewing.
The chrome:// binding is a feature for developers of extensions and built in Firefox features such as the bookmarks manager or downloads window. You can find a list of these chrome:// mappings here. Basically it is a way for firefox to reference files that are on your computer that however might change due to your install path, operating system, or simply the firefox developers choosing to change the physical folder path. These bindings allow developers to always reference the same location.
There are also some other advantages or differences for developers as outlined here. They include the ability that chrome:// url's are exempt from security restrictions - so they can do more things and interact with your browser. They allow the feature to interact or reference other user parameters that might have changed due to customization of themes or locals (regional or language changes) without having to know exactly what the user's customized settings are.