The command line is a place where you type in instructions ("commands") to the computer.
Why is it called a command "line"? Probably because the commands are typed in a line.
What does it look like? Usually a square window on your computer. Historically, this would have a black background.
What is the symbol at the start of the line? The symbol (such as > or $ or ~ ) is called a prompt. This is to prompt you to write something: a command for example.
What is an example of a command? `ls`, which means "Display a list of all my files"
