Convergence & Divergence
Convergence
Rising air (convection) leaves an area of low pressure at the surface, which the higher pressure air surrounding it moves in to replace. Air coming together like this is known as convergence.
Divergence
Conversely, where air at higher altitudes has cooled and become more dense than its surroundings, it will descend. This creates higher pressure at the surface which leads to air spreading outwards. This is known as divergence.