Islamophobia is hate or strong fear aimed at Muslim people, and sometimes at Islam. It is a heavy, public word. You meet it in news, law, and arguments about fairness: an attack, a cruel joke, a rule that treats Muslims as a danger. People do not all draw the line in the same place. Some keep it for harm to people; some also use it when someone goes after the religion itself. Because of that, it can be a fighting word: one speaker uses it as a clear name for prejudice, and another hears it as a way to shut down talk. It is not a soft or casual label. Teachers and papers have used it for about a hundred years; it became much more common in the late 20th century.