What does it mean to "meditate on the law"? I’d love to hear perspectives from different branches of Judaism

I’ve been reflecting on what it really means to “meditate on the law” (as mentioned in places like Psalm 1). I’m curious how this idea is understood across different Jewish traditions—Orthodox, Conservative, Reform, etc.

From a more modern academic perspective, some scholars suggest that the Torah—as in the Five Books of Moses, the first five books of the Bible—may not have existed in the exact form we have today back in ancient times. So that raises the question: what exactly were people meditating on then?

Of course, I understand that not everyone agrees with that historical-critical approach, which is why I’d love to hear how you personally interpret this idea. What do you think it means to meditate on the law? And what is “meditation” in a Jewish context?

Thanks in advance.