Please explain something...

Network Attached Storage

Once you access the website by logging in (usually required for a secure site), then you usually have an interface or software within the browser to use to upload the file, sometimes it may be as simple as clicking a button and finding the file on your computer or simply dragging the file to the open window.

There are quite a few different ways to upload files to a server, you can also use FTP, but that's far beyond the subject of this post, unfortunately..

The data is stored on the Server's Hard Disc Drives or Solid State Drives, so that you, the server, or others can access the data, and that data generally stored is shared unless it's specifically placed somewhere that is secure.

There is also what is known as Torrents, where one could create a torrent upload it to a server and then the file on your computer is left where it is, others download the file from your computer to their computer and now multiple people have a copy, so instead of one person having the file only, like the server, multiple people across the Internet may have the file. In turn, this allows the person wishing to download the file to get parts of the file from multiple people, which in turn gives you faster download speeds, because multiple people are feeding the file to you, instead of just one person.

As a general rule of thumb though, files are stored on the server, unless it's a torrent then it's stored in cyberspace on multiple person's computers.

I hope this answered your question well.

Hah what? When you upload something to a site the data you're uploading if copied to the companies servers. Google has enormous server farms, if you upload something to any Google sites then they are stored on Googles servers. The same goes for most other websites, if you upload a photo or video to Facebook then its stores it on the Facebook.