I want to understand what this means and how it works [on hold]

I want to understand what this means and how it works [on hold]

I had a bit of trouble with making you have +1 life every 20 kills and
someone suggested me this. I haven't put it in xcode yet but if it does
work what does this code mean and how does it work.
I understand what lives++ is and the livescount.text string but not
if (kills != 0 && kills % 20 == 0)
if (kills != 0 && kills % 20 == 0) {
lives++;
livescount.text = [NSString stringWithFormat:@"%i", lives];
}