Bit of an abiguious question that.
Linux comes in many variations called distributions (Hundreds of them), these are then broken down into their core programs & then depending on what GUI front end you have running e.g. KDE or Gnome.
I would suggest visiting somewhere like Distrowatch to get a bit of background on the various distributions before you jump in the deep end & put yourself off.
I would suggest something like Ubuntu as an easy starting point as it is very much like (Cough)M$ in layout & comes on a live CD (No need to install) so if you cannot get on with it move onto the next in your list of distros.