Music theory is the study of the nuts and bolts of music. Quite simply, learn how music works and you can unlock a whole world of creativity.
The problem is that it's often taught in a very boring manner with no examples of actually how to apply it in the really world of music.
This bass tutorial explains the basics you need to know and demos how you might use these ideas in your bass playing.
Make sure to scroll down for more in depth tuition into the specific areas taught.
Half Step (Semitone) Whole Step (Tone)
Half step (or semitone) = 1 fret
Whole step (or tone/whole tone) = 2 frets
Pitch
How high or low a note is. Musicians always talk in term of pitch which can make talking about playing notes on a bass neck confusing. Pitch explains this:

Scale
A collection of notes with a specific formula of whole and half steps.
Bass Guitar Scales: How To Learn And Use Them
Diatonic
A seven note scale with five whole tones and two half tones. These cover the major, natural minor, and modes that come from them.
Relative Minor
Every major scale has a minor equivalent, built from the sixth degree, that contains exactly the same notes.
What Are Relative Major And Minor Scales?
Interval
The distance between two musical pitches and the basis of all melodies (and bass lines).
How To Name Intervals On Bass (Plus Application/Tips/Tricks)
Triad
The first, third, and fifth notes of a scale or mode. Loads of bass lines use these simple notes.
How To Learn And Use Triads On Bass Guitar
Arpeggio (Chord Tones)
Add an octave or seventh to a triad and you get an arpeggio (or broken chord since it's the notes of a chord played separately rather than at the same time).
The Only 4 Arpeggios You Need To Play (Most) Jazz Standards
Chord
Three or more notes played together at the same time.
Bass Chords: Tutorial on Technique, & Soloing (Minor Scale)
Double Stop
Two notes played at the same time.
Tony Levin loves these! How To Play Don’t Give Up, TONY LEVIN (Breakdown & Lesson)
Bass ‘Double Stops’ – What Are They & How To Use Them
Accidentals: flat, Sharp, natural
When you go up a fret you sharpen (#) a note. Going down flattens (b) it. A natural sign cancels an accidental (the sharps and flats). You can get double sharps and flats but they're quite rare.
Reading Music On The Bass Guitar: The Very Basics – Note Names And Locations
Modes
A scale built from a 'parent' scale - usually the major, melodic minor, or harmonic minor.
How to Use Modes: A Guide For Bass Players
Melodic Minor
A scale used a lot in jazz (due to its use of tense and interesting intervals).
Formula: W H W W W W H
W = Whole step
H = Half step
Think major scale with a b3.
Harmonic Minor
Another exotic sounding scale with a bunch of cool modes.
Formula: W H W W H W+H H
Think natural minor with a major 7th.
Inversions
When you place a note other than the root note as the lowest in a chord, you have inverted it. They are represented by slash chords.
A C chord = C (C E G)
C/E is inverted, so E is in the bass: E G C.
Same notes, just turned upside down. This leads to smoother chord progressions and smaller movements between the lowest notes in music.
Harmony
The study of notes played together.
Bass Guitar Music Theory: The 7 Arpeggios From C Major
Harmonising The Natural Minor Scale: Play Bass Lines, Chords & Solos!
How To Analyse Jazz Standard Harmony
Nashville number system
A system of musical notation developed in Nashville. Most known for its labelling of chords within a key.
Roman numerals are used - upper case for major, lower for minor.
CMaj7 Dm Em FMaj7 G7 Am7 Bm7b5
I ii iii IV V vi vii
Chord Progressions
How music is made by choosing what chords sound good together.
The Most Useful Bass Song To Learn EVER? (Arpeggios/modes/chords/improvising etc.)
Key
If a piece of music uses notes from the C Major scale, it is in the key of C. Some songs stay in one key, others change to different keys. Major keys sound bright and happy, minor keys dark, and sad.
Modulation
Modulations occur when you change key. A common key change in pop is going up a tone. Cheesy but effective! Listen to Beyonce's Love On Top for an extreme example...
Circle of fifths
A system of categorising and memorising major and minor keys.
Circle Of Fifths For Bass (How To Learn & USE!)
Non-Diatonic
The description for chord progressions that don't fit to a diatonic key.
Dynamics
Dynamics describe contrasts in music - loud/soft, fast/slow etc. Italian terms are used, such as forte for loud, piano for quiet and crescendo for gradually getting louder.
In practice, non-classical musicians rarely use those Italian words but it's good to be aware of them and to be able to control dynamics.
Time signatures & Meter
The organisation of rhythms into ordered units.
Tighten Up Your GROOVE: Rhythms, Time Signatures, Metronomes & Counting
Swing/Shuffle
A special rhythm for 1/8th notes (and also 1/16ths) used a lot in jazz and blues.
How To Play A 12 Bar Blues On The Bass Guitar
Common Rhythms
Rhythms are so important for bass players. Here are the most common: The Most Common Rhythms & How To Make Bass Lines With Them (Also How To Play In Time)
Syncopation
Rhythms that stress the off beats rather than the on beats. They sound exciting and unpredictable and are used a lot in funk music.
That didn't cover everything to do with music theory but it's a good start! Listen out for these concepts in the wild as that connection is how you will learn to deeply understand music.
Once you go down that road, you'll be able to create easily plus teach yourself music.