(CLAUSE/NOUN1)だけ(で/じゃ)なく(て)NOUN2も as “not only (CLAUSE/NOUN1) but NOUN2 too”
This simple grammar construction is used to clarify that Y, along with X, is what a given statement applies to. This grammar pattern is typically used with nouns but can also be used with clauses. In some cases, NOUN2 may grammatically need to be marked with the particle で, へ, に, と, or から; in these cases, the particle that is necessary of this grammar pattern, も, is placed after the respective particle used. The て in the construction is optional.
Watashi wa kankokugo dake denaku nihongo mo hanaseru.
(I can not only speak Japanese but also Korean.)
Kyou wa suugaku no shukudai dakedenakute, eigo to bungaku no shukudai mo arimasu.
(Today I not only have homework for math but also English and literature as well.)
Nihon niwa kuruma ga aru dakejyanakute, shinkansen de mo ryokou dekiru.
(In Japan, there are not only cars, but you can also travel by bullet train.)