You've learned string DP: LCS, Edit Distance, and their variants. The 2D state represented positions in two strings. But what if the 2D state represents an interval within one string? That's Interval DP.
In Interval DP, represents the answer for substring . You'll see problems like Matrix Chain Multiplication and Palindrome Partitioning. The key difference: transitions combine answers from sub-intervals, not from previous positions. Make sure you're comfortable with string DP before moving on.