Plain-language answer: The near field is the region close enough to an antenna that electric and magnetic fields have not settled into the simple far-field relationship.
Why it changes the path
Coupling to people, cables, structures, and measurement probes can strongly change tuning and local exposure while distance rules depend on antenna size and frequency.
What to observe
Keep objects and operators outside documented clearances and do not use far-field gain or pattern assumptions for close measurements.
The common mistake
Calling every point visible from the antenna “far field.”
Planning boundary
Propagation models and field regions depend on frequency, geometry, terrain, atmosphere, polarization, antenna pattern, and measurement distance. Use them to plan and compare—not to guarantee a contact or installed range.
