What is the purpose of the "schema mode of tables"

[simon.schvartzman]

Surfing the documentation I saw this command:

command cdb_updateTableSchemaMode pTable, pSchemaless

Used to: 

This command changes the schema mode of tables.

but I wasn't able to find what a table being schemaless or not does to the table.

[jasonchan]

A schemaless table allows the creation of a record without predefined schema.
You can create a record with keys that are not defined for the table.
Some project might see a use in schemaless tables if there are dynamically generated data.