Why ATC and AVC get closer as output increase?

Average Total Cost (ATC) and Average Variable Cost (AVC) get closer as output increases because fixed costs are spread over a larger quantity of output. As production rises, the impact of fixed costs on ATC diminishes, making ATC approach AVC, which only includes variable costs. Consequently, the difference between ATC and AVC decreases, reflecting the reduced per-unit burden of fixed costs at higher production levels.