This contains the latest stable Form Tools Core and the standard modules to help you get the most out of the script. You can always add or remove modules and themes later.
There is now an alpha version of Form Tools 3 available. Click here for more information.
Construct your own installation package by selecting the components you want. If you've used Form Tools before this can be a valuable time-saver.
Good question! You may see checksums from time to time wherever there's downloadable content. They're there for developers to confirm that the file being downloaded hasn't been modified in any way and contains only the code that the original developers intended. By and large you don't have to worry about it, but the info is there if you need it.