Words are said, words are heard, the idea's in those words are understood and learned. This is the idea of transmissionism, and it usually doesn't work. It is the reason why lectures and informative texts so often fail to convey ideas—they are implicitly based on a false premise of how people learn.
Comprehension requires something more, often some higher form of engagement. This might be activities, testing, or metacognition, but it is something in excess of simply encountering the facts and expecting that those facts be retained.