In static line training, a line attached to the aircraft deploys the student's parachute as they exit, so the canopy is open within moments of leaving. IAD — instructor-assisted deployment — achieves much the same result with the instructor deploying the pilot chute.
How the progression differs from AFF
Static line jumps start from lower altitude, often around 3,500 feet, and focus first on exits and canopy flight. Once those are consistent, students move to dummy pull practice and then to progressively longer delays before deploying themselves.
It is often less expensive per jump than AFF and works well at drop zones flying smaller aircraft. It typically takes more jumps to reach the same point.
These pages explain what things are so the language makes sense. They are not instruction and cannot substitute for it — skydiving is taught in person by rated instructors at a drop zone, and anything involving equipment handling or emergency procedures belongs there rather than on a web page.