So that is what a column database means

In the video Internals de una base de datos analítica de alto rendimiento: ClickHouse | T3chFest 2019, Javi presented a picture illustrating what really “column-based” database means:

In the above picture, I have got a solid grasp of the concept of a column database. As a bonus, I have also know Apache Arrow. It is one of the contributing submodules in the clickhouse repository.