This is the 303rd most frequent Russian word.
глава
"Chapter" or "head" (depending on context).
In this sentence, 'глава' is used to mean 'head' or 'leader', referring to the person in charge of the family.
Пётр стал главой семьи после смерти отца.
Pyotr became the head of the family after his father's death.
Here, 'глава' refers to a chapter of a book, indicating a division within the text.
Глава книги рассказала о детстве автора.
The chapter of the book talked about the author's childhood.
In this sentence, 'глава' signifies a leader or chief, specifically of a city, akin to a mayor or governor.