convective zone
The convective zone is the Sun's outer layer, where the gas behaves like a pot of boiling water: hot blobs of plasma rise, cool, and sink, carrying heat outward by physically moving rather than by passing light along. It is the part of the Sun's interior closest to the surface we actually see.
It occupies roughly the outer 30 percent of the Sun's radius, from where the radiative zone ends out to just below the visible surface. By this depth the gas has cooled enough — to a few million degrees or less — that atoms grab onto electrons and become very good at blocking radiation. When light can no longer flow freely, nature switches to a faster way of moving heat: whole columns of gas rise, dump their heat near the surface, then sink back down to be reheated. This rolling motion is convection, and it churns far more quickly than the slow radiative zone, carrying energy to the surface in roughly weeks to months.
The convective zone matters because its constant churning, combined with the Sun's rotation, drags and twists magnetic fields and ultimately drives nearly all of the Sun's surface activity — the granules we see, sunspots, flares, and the solar cycle. The tops of its rising columns are visible directly as the bubbling pattern of granulation on the photosphere.
Watch miso soup or a pot of porridge just below boiling: cells of liquid well up in the middle, spread out, and sink at the edges. The Sun's surface shows the same pattern on a colossal scale.
Each granule on the Sun is the top of a convection cell roughly the size of a country.
Not all stars have their layers in this order. Stars much heavier than the Sun convect in their cores and radiate in their outer layers — the opposite arrangement.