And, for almost all Linux/GNU systems, the file extension is of no significance. The file type is identified by the file's "magic number" in its first link.
For example, watch this interchange of a directory and a zip file's name:
Code:
[Peter ~]$ cd tmp/
[Peter tmp]$ file TechnicLauncher*
TechnicLauncher: directory
TechnicLauncher.zip: Zip archive data, at least v2.0 to extract
[Peter tmp]$ mv TechnicLauncher.zip TechnicLauncher # Move the zip file into the directory
[Peter tmp]$ mv TechnicLauncher/ TechnicLauncher.zip # Change the directory name
[Peter tmp]$ mv TechnicLauncher.zip/TechnicLauncher.zip TechnicLauncher # Move the zip file back, renaming it.
[Peter tmp]$ file TechnicLauncher*
TechnicLauncher: Zip archive data, at least v2.0 to extract
TechnicLauncher.zip: directory