What are the essential parts of a looping control structure?

How are these statements different from each other:

(i) break

(ii) continue

(iii) System.exit(0)

Identify all the errors in the following repetitive statements.

while (z < 1 && z > 100)
{
    a = b;
}

Identify all the errors in the following repetitive statements.

while (x == y)
{
    xx = yy;
    x = y;
}