Difference between 2 internationalization (i18n) functions __() & _e()

I’m learning from a plugin development course, and encountered two different internationalization functions:

<?php __('Newsletter Subscriber', 'ns_domain'); ?>

&

<?php _e('Title:'); ?>

I cannot find any reference information on when to use each one of these.

Can you point me in the right direction to learn more about these please?

__() “Retrieves the translated string from the translate() function” without echoing. _e() does the same thing but echos the output.

For more information, take a look at these help articles:

• Internationalization

• Localization

• How to Internationalize Your Plugin

• Internationalization Security