The Major Scale as we know it today is about three centuries old. In 1722, some French guy named Jean-Philippe Rameau wrote the first music theory text. It's the foundation of the major/minor concept that we know today. Prior to this music was organized under the modal rules of Gregorian chant.
Long story. The point is that our system is not new.
It is a seven note (or eight notes if you count the root twice) structure composed of two "tetrachords" stacked one on the other. A tetrachord is a four note group, the first three separated by whole steps and the fourth separated by a half step.
The C major scale: C, D, E, F, G, A, B, C
The first four notes comprise the first tetrachord, the next four are the second tetrachord. Notice that E to F and B to C are half steps. The other notes are a full step apart. This formula (whole whole half whole whole whole half) would make a major scale not matter what not it starts on. I just picked C because there are no sharps or flats that get in the way.
These notes, when arranged in the scale, are called "degrees". The scale degrees are designated with Roman numerals, as such:
Usually, musicians refer to the scale degrees by their number, i.e. "the two" or "the five". But each degree has its own term:
vii: Leading Tone
You will see some of these words later. Remember them. Also,do you notice that some Roman numerals are lower case and some are upper? Do you want to know why that is? Let's find out.