What does No. 2 mean?
According to pencil.com, it all has to do with the HB graphite grading scale used to classify the pencil’s graphite core.
A pencil’s location on the HB graphite grading scale depends on the hardness of its graphite core. The higher the number, the harder the writing core and the lighter the mark left on the paper. As the pencil core becomes softer (through the use of lower proportions of clay) it leaves a darker mark as it deposits more graphite material on the paper. Softer pencils will dull faster than harder leads and require more frequent sharpening.
There might be other markings on pencils. Most pencil manufacturers outside of the U.S. use the letter “H” to indicate a hard pencil. Likewise, a pencil maker might use the letter “B” to designate the blackness of the pencil’s mark, indicating a softer lead. The letter “F” is also used to indicate that the pencil sharpens to a fine point.In reality however, there is no specific industry standard for the darkness of the mark to be left within the HB or any other hardness grade scale. Thus, a No. 2 or HB pencil from one brand will not necessarily leave the same mark as a No. 2 or HB pencil from another brand. Most pencil manufacturers set their own internal standards for graphite hardness grades and overall quality of the core.