The forms of revelations are explained in Q. 42:51 of the Quran. In this verse, Allah says that He reveals to His messengers through inspiration (wahy), by speaking to them directly (kalam), or through angels (tanzil). Inspiration is a form of divine revelation where Allah communicates with His chosen messengers through a spiritual channel without any intermediary. Speaking is a direct communication between Allah and His chosen messenger, where Allah speaks to the messenger directly without any intermediary. And angels are the intermediaries between Allah and His chosen messengers, where Allah sends His message to the messenger through an angel. This verse helps to understand the different forms of revelations that Allah uses to communicate with His messengers, and it emphasizes the importance of these revelations in guiding and leading people to the right path.