Ctrl + c - used to exit line based programs e.g ping command, used to measure the connection speed to an i.p address.

Ctrl + d - Used to inititalize a line based program after inserting the inputs e.g the sort command, used to sort the inputs in alphabetical order.

Programs like sort are line based programs because they read input first before exceuting the instruction.

rm - remove

rm -f - remove files forcefully

rm -rf - remove files in a recursive manner. can delete everything on your pc when it is run by the superuser.