Explore an alternative visual representation of pure multisets using rooted or roofed trees in this 32-minute video lecture. Delve into the world of combinatorics and computer science as you learn how to visualize counting functions geometrically and gain a fresh perspective on multiset arithmetic. Discover useful shortcut notations and examine concrete examples to navigate this new domain. Follow along as the lecture covers introduction, notation for rooted/roofed trees, multiplicity convention with left subindices, counting with trees, closed boxes/nodes, and arithmetic operations using tree structures.