Maybe to a non C++ dev, but a lot of C++ is probably incomprehensible to a non C++ dev, just like there are other laguages that are incomprehensible to C++ devs. To me it makes perfect sense as it works just like all the other operator overloads.

auto - let the compiler deduce return type

operator<=> - override the spaceship operator (pretty sure it exists in python too)

(const ClassName&) - compare this class, presumably defined in Class name, with a const reference of type Class name, i.e. its own type.

const - comparison can be made for const objects

= default; - Use the default implementation, which is comparing all the member variables.

An alternate more explicit version, which is actually what people recommend:

auto operator<=>(const ClassName&, const ClassName&) = default;

if I just want to have less than comparison for example I would:

This one makes it explicit that you're comparing two Class name objects.

if I just want to have less than comparison for example I would:

auto operator<(const ClassName&, const ClassName&) = default;

If I need to compare against another class I could define: auto operator<(const ClassName&, const OtherClass&)