The application will allow you to access your home or work computer and browse your history, bookmarks and open tabs and open them up in Safari. Yes, Safari. This will be one webbrowser company that is entering the iPhone webbrowser game, without an actual webbrowser. However, the app does have a built-in preview option, allowing you to view pages, but doesn't have an address bar.
The purpose of the app will be useful if you leave work or home in a hurry, and need to access your history, using the “Awesome Bar”, which can search parts of the URL, returning results quicker. You can even search for key words within a page, and the “Awesome Bar” will help you narrow your search query down.
The entire application is secured, encrypted end-to-end, so your data will be safe and secure when you are syncing the application with your desktop computer. Mozilla Labs said they will polish the application and submit it for approval to the AppStore.
Mozilla says that they have no plans to release a full-fledge mobile Firefox browser for the iPhone on their Mozilla Wiki page:
Does this mean Firefox will be available on the iPhone?
No. We do not have plans to ship the full Firefox browser for the iPhone. Due to constraints with the OS environment and distribution, we cannot provide users the full Firefox browsing experience on the iPhone. For details, see Mobile/Platforms.
However, with the recent release of the Opera-mini browser, Mozilla might be able to modify their browser to comply with the constraints to release a browser in the future.