What different between HEAD and version 1.1.2 ?

This might be an often asking question but also the forum doesn't help me so much. I use the version 1.1.2 and yesterday I changed my engine to work with the terrainPreviewGui.gui. What I noticed is, that the code of the gui control doesn't work with my engine version. It is written there that the code is for the latest head version. So what is the difference between my version and the head ?? It is confusing to speak about two versions I think ....