As a scientist you learn early to abide by the words of Thomas Jefferson (1820), that "we are not afraid to follow truth wherever it may lead, nor to tolerate any error so long as reason is left free to combat it."
This rule is easy to follow in the sciences because in general the scientist has no stake where the destination lies. (Although this may be true for the Natural Sciences more often than for the Social Sciences.) In fact, the very purpose of scientists is to have a group of people paid for not holding preconceived notions.
The non-scientific world is burdened by more complicated goals.
Philosophers and theologians have an endless capacity to argue about the nature of truth. For most of us the definition is simple: Truth is an observable phenomenon that can be independently verified, not more, not less. Truth and fact are synonyms. The opposite of truth is a falsehood. And if a falsehood is spread with the knowledge that it is a falsehood, it becomes a lie.
Between truth and falsehood lies the indeterminant, a phenomenon that has not been or cannot be declared a truth or a falsehood.
"Planet Earth moves around the Sun." (a fact)
"Joe Biden won the 2020 U.S. Presidential Elections." (a fact)
"Unicorns exist." (an indeterminant)
"There is a heaven." (an indeterminant)
"The Earth is 4,004 years old." (a falsehood)
"The song "Edelweiss" is the national anthem of Austria." (a falsehood)
"Alfred Dreyfus sold military secrets to Germany." (a lie)
"President Barack Obama was born outside the United States." (a lie)
Someone may believe false information to be true. If she spreads this information, she is misinforming others. Someone may know false information to be false. If he spreads this information, he is disinforming others.
Keep in mind that the absence of something (God, U.F.O.s, the Deep State) cannot be proven in principle. Consequently, conspiracy theories can never be fully proven false. Keep also in mind the Sagan standard: "Extraordinary claims require extraordinary evidence." It is not up to you to prove an extraordinary claim false. It is up to the person making an extraordinary claim to provide evidence.