I don't master all of the vocabulary used on cyberspace tools...

[northamericancitizen]

What's a "mirror" ?

[RoyGBiv]

1. Mirror ...

Basically ...

Website A has a file you can download.
Website B downloads that file from Website A and also offers it for download.

Website B is a mirror for Website A.

In practical terms, people and companies often offer software or other files you can download, but this can consume a lot of bandwidth. To pass around the burden, other people, companies, or institutions will offer to "mirror" the files offered by that site. Typically, the originating website or FTP site (FTP stands for file transfer protocol and typically marks a network address that archives files for download.) that holds the file or set of files will offer files and update them on a regular basis. The mirror sites have some sort of automated process running that contacts the originating site to download all the updates and then offer them concurrently. (This will also result in an update delay, which you may see mentioned in the context of mirrors. A mirror site may only update once or twice a day, resulting in an update delay of 24 or 12 hours respectively.) You see this especially with open-source or "free" software that doesn't generate the huge revenue streams of commercial variants, but you see it there some too.

[northamericancitizen]

2. Thanks.

for giving me a specific info that will be added to my own bookmark system.

[Boo_Radley]

3. Also

Also, people sometimes "mirror a disk", meaning that they have a second hard drive that contains an exact copy of the first hard drive, so if one crashes, there is an extremely short down time while they switch to the second hard drive, allowing them to replace the first, failed drive when they get a chance.