To remove the folder with all its contents(including all interior folders):
rm -rf /path/to/directory
To remove all the contents of the folder(including all interior folders) but not the folder itself:
rm -rf /path/to/directory/
To remove all the "files" from inside a folder(not removing interior folders):
rm -f /path/to/directory/
rm stands for "remove"
-f stands for "force" which is helpful when you don't want to be asked/prompted if you want to remove an archive, for example.
-r stands for "recursive" which means that you want to go recursively down every folder and remove everything.
Por Marcos Mendes @marcoshmendes