Datastores are used to describe storage of data. It can be both for input (data sources) and for output (data sinks).

For instance, the following is a datastore describing a PostgreSQL database, with a single table test with a single column a of type int :

<datastore name="mydb" type="postgresql" host="" user="admin" password="mypassword">
  <table name="test">
    <column name="a" type="int"/>

You can find the list of supported datastore types in the datastores section datastores.