mv file.txt ../
However, if you specify a name other than the name of the file, it will move the file AND rename it. Thus, to rename a file you simply move it to the same directory but use a new name such as
mv file.txt new_name.txt
Moving is useful because instead of copying a file (which leaves two versions of the file to take up disk space and introduce confusion), the mv utility makes sure that there is only one copy.
The mv follows the standard syntax of:
mv [option] file1 file2
mv [option] space_delimited_file_list directory_name
There is only one option, the -f option which overwrites the existing file regardless of the permissions.