Components: Select which components you want to remove from Windows. This can be useful if you want to lighten the Windows install. You can easily reduce the install size by even 100MB if you remove a lot of stuff that you don't need. Play with caution though, don't remove anything that you're not aware of. It can be dangerous.
Unattended: Selecting this option will ask you for all the data that Windows generally asks during the installation process. Entering the information here will make the Windows installer an unattended one. You can then boot from the Windows install CD, go out and have a cup of coffee and return to find Windows completely installed and ready.
Options: Changing various Windows install options like default Program Files path, etc. Also includes patches for allowing custom-3rd-party themes, disabling System File Checker, changing networking options and special settings for USB hardware devices.
Tweaks: Loads and loads of tweaks to customize the Windows install. Everything from the size of icons on the Windows desktop to changing the Start button configuration. Also has a Services section which allows you to explicitly enable/disable certain Windows services.
Bootable ISO: This option will allow you to create a bootable ISO image of the Windows installation source which can then be used to install Windows on a computer. You can also burn the resulting ISO image from the application itself.
When working with the installation source, make sure to not remove components which you're not sure of. It's safer to keep something rather than remove it and then having to create another custom disc. After creating the ISO, the easiest way to check if your Windows ISO works fine is to install a Virtual Machine like VMWare or Virtualbox and test in it first. Once you find that the install has been done smoothly, you can burn the ISO to a CD and use it on your computers.