Normally SQL Server stores all of the data for a particular row together, Column store indexes store each column’s data together.
The important thing to notice is that the columns are stored individually. If your queries are just doing
SELECT FirstName, LastNamethen you don’t need to read the long, drawn-out musical tastes. You read less off disk. This is fantastic for data warehouses, where column store indexes have been all the rage for the last few years.
It’s not perfect for everything, though: for starters, when you add a column store index to a table, that table instantly becomes read-only.