Making a directory is no big deal:
$ mkdir ~/temp
But what if you have to make a bunch of directories nested? So what if I had to make ~/temp/temp1/temp2/temp3/temp4 ? Using the -p switch, for parents, the utility will create the structure for you.
$ mkdir -p ~/temp/temp1/temp2/temp3/temp4
This command will create all the directories leading down to temp4.