When you preview the script in your text editor, you should see a box with an elongated oval above it that reads Username and to the right of the box another elongated oval that reads Submit.
Next, note that whatever you type into the box is called a variable because you can type anything into the box. In this case, you type in your username, a simple type of data. Or think of the box and what you type in it as a virtual data room in its simplest terms.
Operators are used to assign a value to your variable based on what you want to accomplish. You want to type in your username, but to know that you need to do this, you see an elongated oval over the box that says Username. Then it clicks: hey, I need to type my username into the box. The terminology VALUE="Username" is the syntax and the = sign is the operator.