What does rm -rf command do on a Linux or Unix?

The syntax to delete file for rm command is as follows:
rm file
To delete five files named file1, file2, file3, file4, and file5, run:
rm file1 file2 file3 file4 file5
To display the name of each file before removing it:
rm -v file
Use the ls command to list files:
ls -l
ls -ld dirname
To list all files and directories for given directory name, try find command:
find dirname
find /path/to/dir/ -ls
find /path/to/dir2/ -type d ls
find /path/to/dir2/ -type f ls

Remove the listed directories and their contents recursively

To delete all files and its directories, run:
rm -r dir1
rm -r -v dirname2
You can force the rm command to ignore nonexistent files and missing operands, and never prompt the user:
rm -r -f myDirectory
rm -r -f -v /path/to/dir2/
Sample session:

Be careful with rm -rf / command

rm -rf (variously, rm -rf /, rm -rf *, and others) is frequently used in jokes and anecdotes about Unix and Linux disasters. The rm -rf / variant of the command, if run by an administrator or root user, would cause the contents of every writable mounted filesystem on the computer to be deleted. Do not try these commands on Linux or Unix like system:
rm -rf /
sudo rm -rf /
sudo rm -rf *

Make a backup

It is critical that you make a backup of all essential data. The data backup must be verified from time to time. Backups allow you to recover data from wrongly typed rm or rmdir commands.

How to prompt whether to remove each file with rm

Pass the -i or -I as follows:
rm -i fileNameHere
rm -i -r dirName
rm -I fileName
The -I option to the rm command prompt once whether to proceed with the command, if more than three files are named or if a recursive removal is requested. Ignore any previous -f option.

rm vs rmdir command to delete directories

The rm command can delete both files and directories (empty or non-empty). The The rmdir command can only remove empty directories. The syntax for rmdir command as follows:
rmdir dirnamehere
rmdir -v dir1
To delete non-empty directories try the rm command:
rm -rf dirName

Getting help on rmdir command

Type the following command at the shell prompt:
man rmdir
rmdir --help
Sample outputs:

Usage: rmdir [OPTION]... DIRECTORY...
Remove the DIRECTORY(ies), if they are empty.
 
      --ignore-fail-on-non-empty
                  ignore each failure that is solely because a directory
                    is non-empty
  -p, --parents   remove DIRECTORY and its ancestors; e.g., 'rmdir -p a/b/c' is
                    similar to 'rmdir a/b/c a/b a'
  -v, --verbose   output a diagnostic for every directory processed
      --help     display this help and exit
      --version  output version information and exit

Getting help on rm command

Issue the following man command:
man rm
rm --help

rm -rf command summary

what does rm -rf command do on a Linux or Unix like system:

1. -r : Remove directories and their contents recursively
2. -f : Force removal of files/directories. Ignore nonexistent files and arguments, never prompt for confirmation.