Interval is the distance between two notes, they can be defined by tones and semitones
Common intervals you should know:
Minor 3rd (m3) = 3 semitones from the root note
Major 3rd(M3) = 4 semitones from the root note
Perfect 4th (P4) = 5 semitones from the root note
Perfect 5th (P5) = 7 semitones from the root note
Diminished 5th (flat 5) = 6 semitones from the root note
Augmented 5th (sharp 5) = 8 semitones from the root note
Octave (P8 or perfect 8th) = 12 semitones from the root note
Keep these terms, they would be used to interpret a lot of formulas that I would be showing you(Lesson 11: Introduction to Chords) in the future, so its better you write them down in your note.
Lesson 1: Introduction to the Piano
Lesson 2: Brief Introduction to music
Lesson 3: Keys of the Piano
Lesson 4: Singing and playing on different keys
Lesson 5: Intervals
Lesson 6: Chromatic Scale
Lesson 7: Circle of Fifths and Fourths
Lesson 8: Key Signature
Lesson 10: Fingering for the chromatic scale
Lesson 11: Introduction to Chords
Lesson 13: Chord inversions
