more File Naming Conventions

unlike Windows, they mean nothing to Linux
certain applications may choose to use particular conventions; Python with .py and gcc with its special extensions, like .c and .o

Pathnames similar to Microsoft (but different!)
directories in pathnames are separated by "/" (and never "\"; backslash has a different meaning)
"pwd" prints the (current) working directory
"cd" changes to a new directory
relative pathnames start with ".", "..", or a directory name.
absolute pathnames start at the root ("/") directory.

"extensions" are purely a convention for humans;