WINSxS is a folder inside C:\Windows. In this folder the Operating System have all roles and features that you can to install and unistall in your system.
If you have space problem in your system you can remove same of this exes and save some space in your computer. For example, you want to remove the exec from GUI shell you can exec this command
Uninstall-Feature Server-GUI-Shell -Remove
Whit the option -REMOVE, you delete the installation folder for this Feature. If in the future you want to install this feature, there isn´t any problem, because if you launch Install-Feature, windows server try to find the installation packet in the WINSxS folder, if this folder isnt in WINSxS, the system download from Windows Update. If you dont have internet you can use the option -SOURCE and install this from a CD with Windows server 2012.