The beginning note of a Major scale is known as its root. However, if you took the same Major scale but started counting from another note of that scale you would be creating what is known as a mode.
Because the Major scale is made up of seven notes, there are seven modes in every key. In turn, each mode is the basis from which chords can be constructed that "harmonize" together.
This interactive diagram allows you to see the notes that make up any mode in every possible key. The stacked blocks of major and minor thirds are guides to help you see the chords that spring forth from each mode.
Each note of a Major scale has a scale degree (indicated with Roman numerals) associated with it. This number tells you which note of the Major scale the mode begins on.
The tetra-chord column show you the four-note chord normally associated with each mode.