what does $options = get_option(‘test_theme’); do?

This sets $options to the value of test_theme in the database, you can go to phpmyadmin and the wp database and the wp_options (if wp is your prefix) and do a search on option_id row and you’ll find it there.

To get this option it should be saved before in the database using add_option() and update_option(), for more info check out the Options API