In hinduism terms the difference between brahman and vishnu

is that brahman is a concept of Hinduism. Brahman is the unchanging, infinite, immanent, and transcendent reality which is the Divine Ground of all matter, energy, time, space, being, and everything beyond in this Universe. The nature of Brahman is described as transpersonal, personal and impersonal by different philosophical schools while vishnu is one of the Trimurti (trinity) in Hindu mythology, and the most popularly venerated god in Hinduism. Vishnu is commonly depicted as being blue in colour and having four arms: with each hand holding either a lotus, a mace, a conch shell or Chakra weapon. Vishnu is the Supreme being or Ultimate Reality for Vaishnavas and a manifestation of Brahman in the Advaita or Smarta traditions of Hinduism.

As a noun brahman

is a member of the first of the four castes of Hinduism, a sacerdotal class.