This summary is not the rule. The rule text controls.
Evidence counts as "relevant" if it meets two simple tests. First, it has to make some fact more likely or less likely to be true. Second, that fact actually has to matter to the case.
This is a low bar to clear. The evidence does not have to prove anything by itself. It just needs to move the needle a little bit, making something seem more or less likely than it would without that evidence.
The second part matters just as much. Even if evidence makes a fact more or less likely, it only counts as relevant if that fact actually matters to deciding the case. If the fact has nothing to do with the real questions the judge or jury needs to answer, the evidence does not qualify as relevant, no matter how interesting or true it might be.
In practice, this rule sets the starting point for what evidence can even be considered in court. Something has to pass this test before a judge will let it in, though other rules can still keep out evidence that is technically relevant.
