With some guitars the neck and fretboard are the same piece of wood, in others these are two separate pieces bonded together. In the latter it is possible, albeit rare, that the fretboard can delaminate from the neck due to too much or too little humidity causing deformation of the woods.

Slots are cut into the fretboard at specific spacings that comprise the tone scale and length.

Frets are pressed into the slots, secured by barbs of the tang, and often times with replacement frets reinforced with CA glue. In this way the frets become integral with thre fretboard and neck.

The nut is placed in a channel at the end of neck where it joins with the headstock. The nut has a slot for each string that serves two essential functions, one, to correctly space the strings apart, and two, to set the elevation of each string at a specific height above the first fret.
The Saddle is positioned on the body of the guitar, the distance between the saddle and the edge of the nut opposing the saddle is the length of the overall tone scale. The saddle sets the string height at the 12th fret.

The neck is deliberately albeit often unecessarily bowed between the 7th and 8th frets, it is said that this allows for the oval vibration of the strings without introducing buzz, however this is, as you will learn, mostly a fabricated cover up for the actual reason which is to compensate for frets that are not in true level, and thus nut slots that are not in symmetry with all fret heights, and so then the saddle cannot be in symmetry with the nut slots, a aggregate of incremental imprecisions into a guitar that consequently plays far below its true potential, and this is true for 99% of all guitars, they lose at least 50% of their potential due to these compounded errors.

The centerpiece, assuming the neck and fretbaord are straight and can be made flat, are the frets. Both the nut and the saddle reference fret height for their correct elevation. When the frets are not in "True Level" (every fret the exact same height as each other, and every fret matching the radius of the fretboard radius which is the only way a fret can be level across the width of the fretboard) then logic says that referencing the first fret that is not level accross the radius is higher at some point, bass, treble, mid and those nut slots will thus be too high for for frets following the 1st, meaning 2nd through 20th because they too doare not level across the fretboard radius, they are in fact out of radius in random from one fret to the next, and so where the nut slot refrerence a low part (say the treble side) of the 1st fret the string now buzzes on the treble side other frets that are higher there than on the the first fret.
It gets worse... the same fret problem makes the same problem when adjust the saddle at the 12th fret. So now, wonky frets make wonky nut slots, makes wonky saddle height/string action... the shop compensates for this by adding relief to the neck, an in bow that elevate the headstock from between the 7th and 8th frets, effectively elevating the strings, shortening the scale length, making the guitar play stiffer, slower, and somewhat out of intonation, the sustain dies quick, and the bends fret out early.
Oh but they still get some buzz, and so the shops file down the frets that cause the buzz. All of this is done with archaic 19th century guesswork flat sanding beams and freehand guesswork filing, it is absolutely impossible to achieve true level frets using these archaic tools and methods. And so it is impossblre to get true nut slots and true string action, and therefor impossible to for the guitar to play and soundto its full potential.
Every guitar out there has been cheated out ofit potential, hence every guitar player has been cheated out of the best their gutiars can be.