How are facts different from opinion?

Short Answer:

A fact is a condition out in the world which is true whereas an opinion is a belief in someone's mind. Opinion may be correct or incorrect but facts can not be incorrect.

Long Answer:

FACT A fact can be defined as an actual condition in the world, a situation which is considered to be true and correct which has been proved and has evidence for it. For example, "The world is rotating on its own axis” is a fact. 

The adjective factual means true, corresponding with reality, correct. One should separate the factual statements from the lies. The result of a natural calamity like Tsunami is a factual account of an event whereas the incidents in a novel might be a fictional story created by the writer unless it is mentioned as a real life story. Factual belief: a belief that can be proved to be accurate. Factual belief takes some time to be proven as true. 

According to Richard Layard fact is a statement that has been proven by scientific research. 

OPINION By definition we may say that an opinion is a belief that has not been proven. It may or may not be true. For example: “My uncle says that drinking tea will lead to indigestion”. In this statement you may notice that it has not yet been proven scientifically that drinking tea may lead to indigestion and the statement is said based on the experience of a particular person. 

A fact is a condition out in the world which is true whereas an opinion is a belief in someone's mind. The difference between fact and opinion is that they are about different kinds of things. Opinion may be correct or incorrect but facts can not be incorrect. "Factual beliefs" in contrast with opinions place facts and opinion on the same level. Factual beliefs have been proven. We know they are true. Opinions have not been proven. They may be true but we cannot be sure.