[In answer to the question “What is the difference between concentration and
focus?”]
Briefly: concentration means undivided attention on some particular task or
object . . . . It is an attention, an activity, devoted to a particular subject.
Now, focus is more fundamental than that. You need to be in focus in order to
concentrate, but focus is the particular “set” of your consciousness which is
not delimited by the particular task, object, or action that you are
concentrating on. You do have to focus on something, but focus is not [limited
to] the continuing task that you are performing. The concept “focus” isn’t
tied to the concrete . . . it remains the same no matter what you are focused
on. It is the “set” of your mind.