Time Machine Issue?

Hi everybody, I am like many others a novice after my new iMac arrived yesterday and I switched off my windows machine for the last time....

Anyway I went and bought a WD My Passport Ultra 1tb external drive last night, plugged it in and checked it was reformatted to work with Mac's. Time machine kicked in and all was well until this morning when I restored all my documents, photos etc (around 35gb). I tried to manually override time machine to begin immediately and I got a message stating that it couldn't find the back up disc?

I checked via Finder and couldn't see anything so I unplugged the WD drive and plugged it back in, hey presto....does anybody know why it might have done this as i'm now concerned that it won't back up in future?

Also could anybody explain in layman's terms, exactly what the icons on the desktop mean? For example my extern drive appeared on there this morning when i plugged it back in?

Appreciate any advice in advance!

Welcome to the forum, and to Macs. If your external drive has a power saving function that spins down the drive, then it may be unmounting because of that power off. I don't know if you can turn that function off, but if you can, do so. The icons on the desktop are just that, icons showing files, folders, whatever you have on the desktop. As a default, OSX shows attached drives as icons. You can then just click on the icon to open the drive. If you don't want them to show, in Finder click on the name in the top bar, then Preferences and on the General tab uncheck where it shows what items will appear on the Desktop. BTW, the Desktop is technically a folder, so that is why you make this change in Finder, as Finder displays the desktop.

Awesome thanks, I will look into the power saving function to see if its that. Cheers!