Understand Columnar Databases

Columnar databases are popular these days. Why are they popular? What do they offer that conventional, row-wise databases don't?

0:00 Introduction
0:16 Movie Theater example
0:22 CREATE TABLE
0:32 Chapter 1: Storage
0:55 Columnar Storage
1:22 Indexing
1:53 Row based retrieval with index
2:11 Column based retrieval with index
2:27 Why do we need indexes?
2:40 Interlude into OS Theory
3:48 Chapter 2: Retrieval
4:45 OLTP Query Execution
5:20 OLAP Query Execution
5:32 Conclusion