What does it mean?
Theoretical understanding of Dhamma obtained through reading, study, and learning.
-from Access to Insight
Why does it matter?
There are plenty of Buddhist books that will tell you (ironically?) that theoretical understanding isn’t that important. What really counts is the insight that comes from meditation. Now, I agree that seeing the teachings directly in meditation IS more powerful than just reading it in a book (or on a blog). But this is true only in the sense that scoring more points than the opponent is what’s really important in basketball. Without good passing and solid defense, you WON’T score more points.
The same is true in the spiritual life. I’ve come to realize over the last few years that we might be underestimating the emphasis that the Buddha put on learning. Right Understanding is the first noble truth. It was the ingredient that the Boddhisatta was missing in his own practice that finally led to enlightenment.
There is one other element to this word that I think is worth remembering: it’s not just learning in the sense of hearing or reading the teaching. It is learning in the sense of memorizing the teachings. Give it a try! I recommend starting with the Metta Sutta. Few are more beautiful.