The truth about the truth is that we can't know always if it is the truth. In other words, we don't have a precise methodology to get a proper/objective verification of every fact or group of facts.
It is normal that people believe in lies, because a lot of people repeated that lie. For example: Kids nowadays believe in Santa Claus because not only their parents are lying to them. Thanks to science we can distinguish some truths, but not all of them, still there is room for speculation. Because of that, religions and mass media have abused of "the truth" that cannot be verified directly, the gray area between fictional possibility and real reality.
We recommend you to find all important/base truths (all important knowledge) in order to create your own believe system, a system that can change over time with the arrival of new and better info.