One of the useful things added is that the language can now define a default <=> operator for your own classes, for example if you had struct Foo {int a; int b;

One of the useful things added is that the language can now define a default <=> operator for your own classes, for example if you had struct Foo {int a; int b;} previously you'd have had to define your own comparison operators such as: bool operator<(const Foo& foo) const { if (a < foo.a) return true; if (a > foo.a) return false; if (b < foo.b) return true; if (b > foo.b) return false; return false; } .. and all the other comparison operators that you needed. But now, you can just say: auto operator<=>(const Foo&) const = default; and the compiler will automatically generate all the operators for you.