It process will be chrosome banding. In case of this each and every chromosome has a banding pattern and band is numbered to beneficial for identification a particular point of a chromosome. This method of mapping a gene to a specific band of the chromosome is called cytogenetic mapping.

This is a specialized branch called Cytogenetics, now evolved as Cytogenomics. You need to read basics of chromosomes, refer to guidelines of chromosome nomenclature.

ISCN - HGVS Nomenclature (hgvs-nomenclature.org)

this should be useful