With different pencil grades you can draw very light and very dark, almost black, tones.
The softer the pencil the darker the tone value, the harder the pencil lead the lighter the tone value.
But also with just one pencil you can make a lot of different
shades of grey.
The more pressure you apply the darker it gets.
Here is a small variate with a 2B pencil:
In addition to that, the application of different strokes and lines mean a different outcome.
Here is an expample of rough strokes:
simple lines, crossing lines, round, circular moves.
It is also possible to mix various techinques or simply vary the
length and how close the strokes are applied.
When it comes to very realistic drawings the strokes are applied smoothly and closely to each other so you cannott tell one stroke from another.
With additional blending the possibilities are alsmost unlimited.
Here is an example of blended strokes: