Having some distrust in Wikipedia is healthy; you certainly shouldn’t take it as the final word about facts you’re depending on the accuracy of. But, it is very often a good starting point for learning about a new subject.
Spending a minute or two reading that “source code” article (or another version of it which is likely available in your first language) would give you a much better understanding of the concept of source code (which is a prerequisite for understanding what “closed source” means) than any of the answers in this thread so far.
“When it comes to software and copyright law, I trust pseudonymous internet randos more than Wikipedia.”
Yes
Having some distrust in Wikipedia is healthy; you certainly shouldn’t take it as the final word about facts you’re depending on the accuracy of. But, it is very often a good starting point for learning about a new subject.
Spending a minute or two reading that “source code” article (or another version of it which is likely available in your first language) would give you a much better understanding of the concept of source code (which is a prerequisite for understanding what “closed source” means) than any of the answers in this thread so far.