An extremist Muslim is one that will kill or explode you as commanded by the Quran.
A radical Muslim is one who vocally demands you be killed or exploded, but won’t do it themselves. They’ll get the extremist to do it, as commanded by the Quran.
A moderate Muslim is one who believes quietly that you should be killed or exploded. They argue for the acceptance of Islam in public and call it a religion of peace. And continue to attend their radical imam’s mosque and pay the zakat so they can fill their basements with weapons to arm the radicals and extremists. As commanded by the Quran.
A liberal Muslim is one who doesn’t believe you should be killed or exploded, and has either rejected or hasn’t ever actually read the Quran to know what they’re supposed to be doing. The others correctly call the liberal Muslim an apostate as commanded by the Quran, and have the extremist kill or explode them, also as commanded by the Quran.