Everything C++
Modern C++ usually refers to C++11, C++14, C++17 and later. C++11 was a revolution and it actually became another language compared to classical C++ as C++98 and before.
Modern C++ Features by Anthony Calandra
[1] GeeksforGeeks
[2] The Complete Practical Guide to C++ STL by Abhishek Rathore.
[3] cplusplus.com
[4] cppreference.com
[5] "Beginning C++ Programming - From Beginner to Beyond" course by Frank Mitropoulos on Udemy.
[6] "Concurrency with Modern C++" course by educative.io.