Like I said, a comment. No, I didn't forget, I did that for a reason. Remember how I said that if you didn't use quote marks it would be thought of as a variable. There are different things you can store as variables. They can also contain numbers and most symbols.
Numbers are numeric values.
They are just numbers, negative or positive, whole or a decimal. They are more helpful later on. Null null null is nothing, zilch, not even zero, or false. I think that is all. And I think that variables have to be from 1 to 10 digits in length and have to start with a letter.