== -> equals to
!= -> not equal to
So if you eg put in your logic: '1'=='1'
Then the template will go further via the succesful exit of your step branch (since 1 equals 1).
In the template, it's not '1'=='1' but '{-FieldData.FieldData-|-●2●1●5●1●8●1●-|-tp-8365-}'==''
So the template will go further via the succesful exit if the output of your parsing step equals to blank(''),
in other words, when the text "captcha error" was not found during parsing. When it is found (parsing step is not equal to blank), the template goes via the unsuccesful exit back to enter the captcha again...
Think you can find these things in the zenno guide though.