It is bundled with acrobat pro etc.
It is used to produce dynamic forms (fillable pdf's, and similar) along similar (but more powerful) lined to those permitted in acrobat itself..
your install of acrobat should also have installed an icon for livecycle in your program files.
Or you can access it from acrobat by clicking on the purple forms icon.
It's a great tool, and if you know your way around acrobat you should do ok with it.
The help file is useful, also two books PDF forms using acrobat and livecycle (also claled PDF forms Bible) and creating dynamic forms with adobe livecycle (by j p terry)
enjoy!