Whatis the difference? please help me out

lokenbo2 

If you look up the Roku wiki, there is a good list of all of the different models of Roku along with the model numbers of each.  That way you will know what the latest models are.  Then you can look for those models when you are purchasing, so you won't buy a model that may seem like a good deal but may not be if it turns out to be a really old version.