mirror?

just curious ut i am trying to download “garrysmod jet” from garrysmod.org and it says “This file is being mirrored. Please try again later.”
i am just wondering what does this meen?

this is going on with all the files…and i don wanna try again downloading an hour from now, its kinda late where i am

ok, the addon i was trying to download is back up and working,

i know what gives