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Everything that JohnV said plus, the patterns are movable, just like barre chords. So once you know a pattern in one key, you can move it up or down the fretboard to change keys.
There are seven different modes (moods) which correspond to the 7 (A B C D E F G) possible starting notes of a pattern within the scale. These are also moveable.
You will need to know where those 7 notes are located on the low E and A for the majority of chords. It will also be helpful to learn the note locations on the D string too, but it can wait a while.