math.random() and comparison operator clarification

I know Math.random() generates random numbers, my question is:

1.What is going on by comparing it to .5 (or 50%)?

2.How does that trigger the if statement into working?

3.Is Math.random() getting its numbers from the variable1?

 variable1 = 8;
 while (variable1 > 0){
    If(Math.random() < .5){
    variable1--;
    }
 }