I am reading Michael Aschbacher's Finite group theory textbook. Exercire 1.6 makes me confused.
1.6 Let H is normal subgroup in G. Then the map L->L/H is a bijection between the set of all subgroups of G containing H and the set of all subgroups of G/H. Normal subgroups correspond to normal subgroups under this bijection.
It is not clear for me what is L. I perused previous paragraphs but didn't find any relevnt information. I will be really thankful if someone would help me to understandhow to solve this exercise.