The site tour uses the term scientific skepticism. Presumably this is the source that you are asking about.
The Tour points to the Welcome to New Users FAQ question.
The Welcome to New Users FAQ question expands the meaning:
This site is about applying scientific skepticism. We only accept answers based on independently verifiable applications of the scientific method ("facts").
In other venues, people can get lost in long discussions about what should theoretically happen — think about questions such as: "Will you get more wet if you run or walk, in the rain?" —, but not here. We don't allow such speculation, we expect only scientific trials of these matters to be discussed, and answers to be fully based on those.
Please be very aware of the difference between theory and practice, because users will challenge you on this!
It points to the Wikipedia definitions of scientific skepticism:
Scientific skepticism or rational skepticism (also spelled scepticism), sometimes referred to as skeptical inquiry, is an epistemological position in which one questions the veracity of claims lacking empirical evidence. In practice, the term most commonly references the examination of claims and theories that appear to be beyond mainstream science, rather than the routine discussions and challenges among scientists. Scientific skepticism differs from philosophical skepticism, which questions humans' ability to claim any knowledge about the nature of the world and how they perceive it, and the similar but distinct Methodological skepticism, which is a systematic process of being skeptical about (or doubting) the truth of one's beliefs.
The proposition of whether Trump ordered tear gas can be established through empirical evidence, and it is a widely-believed claim, so it is on-topic here.
The proposition of whether Trump ordered tear gas for a particular reason cannot be established through empirical evidence, so it is off-topic here.