To effectively learn ROOT, a C++ library used primarily in particle physics, a solid understanding of C++ is essential. Key concepts include object-oriented programming principles such as classes, inheritance, pointers, and functions. Familiarity with data analysis in particle physics, including various plots, types of variables, and statistical fitting functions like Breit-Wigner, is also beneficial. While ROOT can be challenging for beginners, mastering C++ fundamentals is crucial before diving into ROOT's functionalities. Additionally, resources like "Object-Oriented Programming in C++" by Robert Lafore are recommended for learning C++.