What happens when if statement goes true (in this code)?

There is a problem in codingbat.com which you're supposed to remove "yak" substring from the original string. and they provided a solution for that which I can't understand what happens when the if statement goes true!

public String stringYak(String str) {
  String result = "";

  for (int i=0; i<str.length(); i++) {
    // Look for i starting a "yak" -- advance i in that case
    if (i+2<str.length() && str.charAt(i)=='y' && str.charAt(i+2)=='k') {
      i =  i + 2;
    } else { // Otherwise do the normal append
      result = result + str.charAt(i);
    }
  }

  return result;
}

It just adds up i by 2 and what? When it appends to the result string?

Link of the problem: https://codingbat.com/prob/p126212