Explore the concept of sketching in big data through this 50-minute lecture by Jelani Nelson from Harvard University, part of the Simons Institute Open Lecture Series. Delve into the fundamentals of sketching, starting with a simple example and progressing to more complex applications like approximate counting and frequent items in streaming models. Learn about known algorithms, reductions, and proof techniques used in graph streaming problems. Discover how to handle data insertions and removals in streaming scenarios, and understand the challenges of querying in this context. Gain insights into the practical applications of sketching techniques in managing and analyzing large-scale data sets.