Every word (the thing what author calls a "variable") has a binding. In short, it's a pointer to the namespace where value associated with that word resides. B

Every word (the thing what author calls a "variable") has a binding. In short, it's a pointer to the namespace where value associated with that word resides. Blocks can nest any other value, including words. At any point in runtime you can change this pointers (bound word to some value) for every word in a block or for separate words.