At the time it was just one among many. I first encountered it using telnet info.cern.ch, which was a line mode browser. There wasn't much to see other than links to other web servers. Usenet was much more important and gopher had more content. But when I first saw a web page on Mosaic, with pictures and rendered text, it was mind blowing.

So Mosaic was also a local file browser? I always thought this stupid idea to combine web and local file browsing into one app was invented by Microsoft and then later adopted by KDE (Konqueror)...

In the early days web sites would often be down, or you might need to copy pages or a whole site to disk for access offline, especially on laptops. Even in the early 2000s I used to take dumps of HTML documentation with me on disk or thumb drive, because even if I had internet access at a hotel or customer site I wouldn't have access back to the company network. It was an essential feature.

I constantly use this feature, even today. I regularly use Dash, and when I’m working on a personal project I like to use SiteSucker or safaris WebArchive save format to collect the docs, information and blog posts I need.

With this, I can then turn off my internet and dive deep into the task. It’s how I learn!

About the only missing thing I have is an offline cache for language package managers — I use so many that it’s a bit difficult. I should really go look for some Docker images that have already tackled it...

It is a nominal feature that exists in part to supplement the file: protocol for viewing local web pages. The UI is invariably basic, typically identical to the browser's FTP interface.

Many (most?) web browsers support this, even today.