whenever we execute a command, it shows its output on the terminal window only. But, if you want this output to be saved in a file then concept of redirection comes in picture.
(Greater than) is used for redirecting output to a file
so whenever we use >, the output is saved to a new file. But if you want to redirect its output to an existing file then you have to use >> else your previous data will be lost.
TO verify this you can see below screenshot.
Now appended content screenshot
< (less than) is used for redirecting input to file.
if you want to do some operation on the file. like counting number of words, lines.. etc in a file.Note the difference, when you are using redirection, your file name is not shown because during redirection file is sent anonymously.
you can also easily combine STDIN and STDOUT. e.g. you want to process a file and want to save the output into a new file then this combination is useful.
you can also use 0> for STDIN and >1 for STDOUT.
ls video.mp4 2> error.txt
If video.mp4 is not present in your file directory then you will get an error-
ls: cannot access 'video.mp4': No such file or directory
and this error will be saved to a new file error.txt.
ls -l video.mp4 file.txt > myoutput 2>&1
You can read about pipe here.