A little about MODES
Learn about "chord-scale compatibility", i.e., the C major scale is the Ionian scale (I) C-D-E-F-G-A-B-C, ... the II scale in C major is the D Dorian scale (D-E-F-G-A-B-C-D), and so on with III (Phrygian), IV (Lydian), V (Mixolydian), VI (Aeolian), and VII (Locrian)
Memorize all these scale patterns and practice shifting between them keeping in mind where you are relative to your root key (i.e. I, II, V, etc). Practice intervals, arpeggios etc across these scales, ascending, descending, also ascending on only 2 strings up 2 octaves, then descending down a different area of the fretboard. Hours of fun. PLUS, you'll see interval, harmony and chord patterns and relationships you may not have previously noticed.
This is most easily seen in the chart below. I'm not a professional musician, so anyone more knowledgeable out there: please correct me if there's something wrong here.
The Dorian pattern is offset to the left on purpose, because I want to remind myself to start with my second (index) finger for the Dorian scale. For all other patterns, if the first dot is in the bottom left position, start with the second (index) finger. If there's an open fret space left of the first dot, start with the 3rd (middle) finger. The reason for this is that if you follow this convention, then moving up or down a single string (rather than using the next string up or down) will always have the pattern continue 1 whole tone up from the last note in the 2 or 3-note section of the pattern... This makes it much easier to move around the fretboard with accuracy.
A little about CHORDS
the basic triad consists of the root (1), third (3), and fifth (5).
To understand major vs minor, and "perfect" vs diminished vs augmented, you should know that in the 8-note scale (including the octave), only the 4 and 5 can be diminished (flattened a half tone). All the other notes (2, 3, 6, 7) are "minor" when flattened a half tone. Sharpening a half tone yields an augmented "X" (2-7).
So, with this in mind, and using the C Ionian scale (C D E F G A B C) the main triads are:
MAJOR: C E G
MINOR: C Eb G
DIMINISHED: C Eb Gb
AUGMENTED: C E G#
Now, if you add in a fourth note to the chord (commonly the 7th) you need to know that in the notation, one "maj" refers to the 7th being major (a half-tone below the octave) and one "min" (or just "m") refers to the 3rd (being flat). The 3rd default is MAJOR and the 7th default is MINOR... SO:
C Maj 7: C E G B (C major triad + major 7th: B is a half-tone below C)
C Dominant 7 (Or just C7) : C E G Bb (C major triad + minor 7th)
C min 7: C Eb G Bb (C minor triad + minor 7th)
C Diminished 7: C Eb Gb Bbb (C diminished with double flat B, which is equivalent to an A)
C Minor Major 7: C Eb G B (C minor triad + major 7)
Then you can get into 6ths, 9ths, 11ths, 13ths, sus4 etc etc...
A good book that explains this (and much more) is the Total Jazz Bassist by Overthrow & Ferguson.
I hope that helps.