Return a Sorted Array Without Changing the Original Array clairfication needed

Tell us what’s happening:
from the examples in the last task i answered the question however i dont understand one bit of it
x.sort((a,b) => a - b) - what is thr - actually symbolising here? a minus b or just a comes before b?

**Your code so far**
function nonMutatingSort(arr) {
  // Add your code below this line
let x = globalArray.concat(array)
x.sort((a,b) => a - b)
return x

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Link to the challenge:

Take a look at the definition of sort() and how the compare function works.

- isn’t symbolizing anything. We are subtracting one value from the other.