Layer names are not part of ArchiCAD, but rather part of the file you are working on. If you started a fresh project from a Template in the start dialog - then those layer names were created for the Italian version of ArhicCAD and you would have to contact Graphisoft Italy to ask them what their logic is. The USA template uses entirely different layer names... as does the INT (International) version, for example.
If you opened a file that you received from someone else...then those layer names come from that person.
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