Rust's `const` is an actual constant, like 4 + 1 is a constant, it's 5, it's never anything else, we don't need to store it anywhere - it's just 5. In C++ `const` is a type qualifier and that keyword stands for constant but really means immutable not constant.
This results in things like you can "cast away" C++ const and modify that variable anyway, whereas obviously we can't try to modify a constant because that's not what the word constant means.
In both languages 5 += 3 is nonsense, it can't mean anything to modify 5. But in Rust we can write `const FIVE: i32 = 5;` and now FIVE is also a constant and FIVE += 3 is also nonsense and won't compile. In contrast in C++ altering an immutable "const" variable you've named FIVE is merely forbidden, once we actually do this anyway it compiles and on many platforms now FIVE is eight...
This results in things like you can "cast away" C++ const and modify that variable anyway, whereas obviously we can't try to modify a constant because that's not what the word constant means.
In both languages 5 += 3 is nonsense, it can't mean anything to modify 5. But in Rust we can write `const FIVE: i32 = 5;` and now FIVE is also a constant and FIVE += 3 is also nonsense and won't compile. In contrast in C++ altering an immutable "const" variable you've named FIVE is merely forbidden, once we actually do this anyway it compiles and on many platforms now FIVE is eight...