In this era of broadband net connections to home, office and street, the web user experience is generous.  Because of this, we expect our videos to stream and our email attachments to make it through every time.  In general, whatever we want to move, no matter how large, we expect it to get from point A to point B without trouble.

Sometimes that just doesn't happen.  Why?  The answer is usually bandwidth.

Between point A and point B is a whole lot of connectivity. The connectivity is measured in bandwidth.  In the exact same way a pipe in your home is measured in diameter and length, bandwidth is measured in kilobits per second, or kbps.

Pipes that carry water have a maximum capacity and this can be anticipated and engineered for.  A 1" diameter pipe can carry less water across time than a 2" diameter pipe and so on.  The same rules apply to internet bandwidth.

Bandwidth costs money, so some servers or services have more / better bandwidth than others.  For example, FilesDirect has more than enough to make sure large file transfers happen reliably.  Each different website on the internet is a server and the speed at which you receive the content it serves to you is greatly affected by the amount of bandwidth the web server operator has bought, or "provisioned".

That's just the first pipe in the chain leading back to you, though. Between you and that server are many pipes.  Some are huge and operate at nowhere near capacity.  But some are overloaded, slowing your transfer down just like an overloaded drain pipe will work slowly.

What's more, the connectivity's total bandwidth is constantly changing, which is why a download attempt that fails one minute might succeed the next, or vice versa.

In charge of your user experience, but hidden: that's bandwidth.