SSL certificates are used within web servers to encrypt the traffic between the server and client, providing extra security for users accessing your application.
Find recursively searches a location for files or directories. It has many flags to output only the files that you are looking for.
Linux and all version of unix (including MacOS) have a very rich command line that can be used in many different ways to form very powerful commands.
GNU/Linux is a free operating system that has been released under the GPL (General Public Licence).