This is the first installment of "things you ought to know." There may never be any more, so at least the first one will be numbered.
Backslash vs Forward Slash
You ought to know the difference between a backslash and a forward slash. Look up at the address bar of your browser right now. Those are forward slashes. Any web address will contain forward slashes. If you state a web address with backslashes, it is likely wrong. Since forward slashes are so common in this context, we usually just call them slashes. Here is how you can know which is which:
Start with a vertical line: |. Think of it as standing on two feet like a person. Now, since we read left to right, a forward slash will look like it is leaning forward: /. A backslash will look like it is falling backwards: \. Got it?
Regarding 'rithmetic, you ought to know that a forward slash usually denotes division: 1/2 means "one-half" which is the same is "one divided by two."