This is the 5827th most frequent Russian word.
разделов
"Разделов" means "sections" or "divisions" in English.
The word 'разделов' is in the genitive plural form, denoting possession or quantity in relation to 'много' (many).
В книге много разделов, каждый из которых посвящён отдельной теме.
The book has many sections, each of which is dedicated to a separate topic.
'Разделов' here is also in the genitive plural form, indicating a partitive sense, as 'несколько' (several) is quantified.
Мы изучили несколько разделов этой главы.
We studied several sections of this chapter.
Although 'разделов' is not directly in the sentence, its modified form 'разделы' is used in the plural nominative to indicate the subjects added.