if you want minecraft worlds and mods:
worlds: download the world save you want and unzip it. (you need a unzipping program like WinRAR to do this) extract the file you downloaded, with WinRAR and you should have a folder. this is the world. now bring up the start menu and type %appdata% into the search bar, a flie called roaming will be there, open it and search for a folder called .minecraft.
open that and there will be a folder called 'saves'. put the world folder into there and when you play minecraft it should in your world selection
mods:download the mod, and like the worlds extract it with WinRAR. now you will have a folder. do the %appdata% thing again and go into .minecraft. theres a folder called bin open that and there will be a file called minecraft, open that delete the META-INF folder and drag whats in the extracted mod folder into the minecraft file
I think he means powder toy worlds to a folder hwere you can click on it and it will load it so you can access it without internet.