Modern C++ introduced uniform initialization with curly braces. Write int arr[]{1, 2, 3}; without specifying size. The compiler counts your initializers and sets the size to 3 automatically.
This syntax reduces redundancy. Instead of int arr[3] = {1, 2, 3}; where you state the count twice, let the compiler figure it out. One less place to make mistakes. The uniform initialization syntax works consistently across C++.
Arrays, structs, and classes all use curly braces. Learning it here transfers to other parts of the language.