This particular passage explains the so-called command that God gave Adam. Basically, God allows Adam to do whatever he pleases in Paradise. The "till and keep" of the land doesn't really amount to much. The "work" that he does is merely gathering food. Gardening the land isn't necessary as God has promised that the fruit will always be plentiful. Even so, these are conditions that God has put on Adam's (and Eve's) freedom in Paradise.