Can somebody explain the theorem $7.2$ in Lang's Algebra
Questions:
$\bullet$ What does it mean ''Let $m$ be the product of all primes unequal to the characteristic dividing the degree $[K:k]$'' really all primes, that is infinity ?
$\bullet$ Why is there a tower of subfields between $F$ and $KF$ such that each step is cyclic of prime order ?