The headshot 
For casting
- Head and shoulders, still, on a clean backdrop.
- A clear, current likeness — what you'll look like walking into the audition room.
- The job: get you shortlisted before anyone's seen you move.
- Studio-lit, simple, no distractions from the face.
The portfolio / movement shot 
For your book
- Full or near-full body, showing line, extension, control.
- Often on location, or with more room to move than a headshot setup allows.
- The job: prove technique and physicality to an agency or company.
- More dynamic — mid-movement, held positions, a sense of the body in space.