Mind activity is the entire sphere of consciousness. This can be confusing for people reading Zen texts. A sense of separation can breed fixation and attachment. The whole relationship, not the analyzed parts, is the critical point. Wholeness is only found in the wholeness of relationship.
Attention is emphasized in the introductory teachings about mindfulness.
Awareness is the fruit of mindfulness practice. It is a step beyond attention which explores our living experience without the shackles of self-conscious separation. A common metaphor for the difference between attention and awareness is the flashlight and lamp. If we enter a dark room, we can use a flashlight to illumine very clearly a small area of the room. Whatever is within the beam from our flashlight is clear and distinct, but we cannot sense the room as a whole.