This summary is not the rule. The rule text controls.
If someone wants to testify about something in court, they need to show they actually know about it firsthand. This means they saw it, heard it, or experienced it themselves, not just heard about it from someone else. There has to be enough proof to convince the judge or jury that the witness really does have this firsthand knowledge.
The witness can prove this personal knowledge just by testifying about it themselves. For example, a witness can simply state "I saw the car run the red light" and that statement itself can be enough to show they were there and witnessed it.
This rule does not apply to expert witnesses. Experts are allowed to give opinions based on their training, experience, and knowledge of a field, even if they did not personally witness the events in the case. That type of testimony is covered under a different rule.
