Spirited definitions...
Attention is when interest is captured.
Concentration is when Attention is narrowed.
Focus is when Concentration is intensified.
***
Merriam-Webster dictionary:
Attention
- the act or power of carefully thinking about, listening to, or watching someone or something
- notice, interest, or awareness
- special care or treatment
Concentration
- the ability to give your attention or thought to a single object or activity
- the ability to concentrate
- the act of giving your attention to a single object or activity
- a large amount of something in one place
Focus
- a subject that is being discussed or studied
- the subject on which people's attention is focused
- a main purpose or interest
- a point at which rays of light, heat, or sound meet or from which they move apart or appear to move apart
- the point at which an image is formed by a mirror, a lens, etc.