Belief - AbsoluteAstronomy.com

Belief is the psychological state in which an individual holds a proposition

Proposition

In logic and philosophy, the term proposition refers to either the "content" or "meaning" of a meaningful declarative sentence or the pattern of symbols, marks, or sounds that make up a meaningful declarative sentence...

or premise

Premise

Premise can refer to:* Premise, a claim that is a reason for, or an objection against, some other claim as part of an argument...

to be true

Truth

Truth has a variety of meanings, such as the state of being in accord with fact or reality. It can also mean having fidelity to an original or to a standard or ideal. In a common usage, it also means constancy or sincerity in action or character...

.
The terms belief and knowledge are used differently in philosophy.

Epistemology is the philosophical study of knowledge

Knowledge

Knowledge is a familiarity with someone or something unknown, which can include information, facts, descriptions, or skills acquired through experience or education. It can refer to the theoretical or practical understanding of a subject...

and belief. The primary problem in epistemology is to understand exactly what is needed in order for us to have true knowledge.