What does the verification code (captcha) do?
This test verifies whether the entries have been made by a human or a machine.
Generally speaking, machines (software programs) cannot read the sequence of letters and numbers. This prevents spambots from making entries in directories and filling them with gibberish or inserting malicious content (computer viruses, worms, Trojan horses etc.)
If the code is illegible to humans, a new code can be requested. Upper/lower casing is not important when entering the code.