Not in this situation.

The problem with Math.sign is that it only works on numbers, while we might be comparing arbitrary comparable objects which doesn't admit a numeric rank.

It is performing the sign function, which Javascript does not natively support (yet*, although it is being added: Math.sign(c) would give the same result in a Javascript environment which supports the new function). You will also get a number's sign if you divide it by its absolute value; since Javascript does support the abs function, you could write c / Math.abs(c) to get the same result.

The ternary statement there is equivalent to writing,

if (c < 0) {
  return -1;
} else if (c > 0) {
  return 1;
} else {
  return 0;
}

Since it's inline, you can write a statement such as return a ? b : c or result = a ? b : c and it's much simpler and more concise than writing the equivalent code.

*Actually since CodeWars supports ES6 now, Math.sign will work in the JS framework. For use in web programming, though, browser support of the feature is still limited.

That's an "inline if" or "ternary" statement.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator