Check out our forms docs. You can have some of the fields always show and some of them show conditionally (using progressive profiling). Most of our customers use a combination of ...
It kinda depends on how you've structured your forms, but here is our docs page: http://docs.marketo.com/display/DOCS/Configure+Form+Progressive+Profiling
Progressive Profiling means you are changing the fields a lead is entering if they've visited the form multiple times. It helps you gain more data about someone without having them...
It's a bug, it shouldn't set the content for that segment in this case. The consequence is that the checkmark means it's saved out the content for that segment.