In most cases your message is submitted to your lawmaker in a manner that is similar to sending an email message to them. The message includes your name, address, and email address. This allows your lawmaker to determine that you are, in fact, from their district or state and gives them a way to get in touch with you.
Here's an example message:
I am a voter in your district. I support the legislation H.R. 1446. I encourage you to vote for it. Thanks to Countable.us, I will be receiving updates on how you vote on this and future legislation.
More about this bill: H.R. 1446: REAL Space Act
As a world leader, the U.S. should be at the forefront of space innovation. Returning to the moon and establishing a base there would be a massive accomplishment, creating momentum for further exploration in the final frontier.
-- Countable makes it easy for your Constituents to learn about the issues they care about and let their Representatives know how they feel. Learn more at http://www.countable.us/about/congress or at firstname.lastname@example.org.
In addition to the above message, your full name, email address, and address are submitted to your lawmakers. Congressional offices require this info in order to submit messages electronically.
How do I know it's been submitted?
Great question! In most cases your lawmaker will respond to your inquiry directly, though not necessarily immediately.