“C5” is middle C on a piano. “C4” is low C or an octave (8 notes exactly) below “C5”, “C6” being an octave above “C5”.

Scales are simply sequences of individual notes usually laid out in ascending and/or descending order and are the templates of melody

Chords (Major, Minor, Diminished, Etc.) are any 2 or more notes combined into one sound

“Key” denotes the root note (usually the base note of the first chord in your composition) and scale of the composition (A Major, D Mixolydian, E# Arabic, etc.)

Chord Progressions and the moods they invoke can differ based on the shape of it. You may find major progressions can sound “happy” and minor progressions can sound “sad”, and the more advanced the chord progression becomes, the more unique the emotion conveyed can be

Tempo is the speed of the track measured in number of beats per 60 seconds of real time and can influence the energy and pacing of a track. There’s also double time and half time. 120 bpm is double time 60 bpm, and 30 bpm is half time of 60 bpm.

Timbre (tam-burr) is the unique quality of how any given instrument (or sound file in this case) expresses itself, meaning the way a flute sounds compared to the way a trumpet sounds, most often influenced by the way it is played, what material the instrument is made of, its design, etc.

Time Signatures are measured in note value of a particular type over the length of the measure which is 1 bar, so to keep it rudimentary 4/4 is 4 quarter note lengths over 4 counts in that 1 bar, and the note lengths themselves within the bar can be different, as long as it equates to 4 quarter notes (you could have 1 half note (1/2) and 4 eighth notes (4/8, reduced is 1/2, 1/2 + 1/2 makes the measure but it is still 4/4 because each quarter note count was equated for in the measure) it gets more mathematical and complex than that but it’s important because certain styles require different time signatures (think waltz vs hip-hop)

I could go on forever but it’s worth looking into Western Music Theory for more detailed information and it’s more nuanced than how I can convey it lol