Is there a site with method and command description like Java Oracle for c++?

Materials may vary depending on the c++ compiler in addition to the ISO standard.

Typically, you need to know whether it is gcc or visual c++.

Related to ISO standards https://en.cppreference.com/w/

GCC https://gcc.gnu.org/onlinedocs/

VC++ https://docs.microsoft.com/ko-kr/cpp/?view=vs-2019#pivot=langlib&panel=langlib1