Liquibase export data

I am using liquibase-3.0.0 with mysql 5.6 and ubuntu and trying to run some liquibase commands but have some issues:

Following documentation, Export Data from Database

 java -jar liquibase.jar --changeLogFile="./data/<insert file name> " --diffTypes=“data” generateChangeLog

What is diffTypes=“data” representing here? Its returning the following xml file:

With diffTypes=data(without quotations)

its returning the schema of database in xml that includes script for table creation etc without data 

Shouldn’t this be returning the data present in the tables not just table definitions?

How can I use liquibase to export data(“table contents”) ?

Does Tag and rollback actually work on the schema and not on data contents?