The Forms Designer permits you to design your form including its layout, workflow and logic. When you launch the designer from the Ribbon menu in SharePoint it will open in the browser and you will be presented with the following toolbar.
It provides you with a number of options:
- Save and exit
Save does exactly that, it saves any changes you make.
Save and exit
Save and exit will save your change sand exit the Designer.
Well you can guess what this does :)