A footing is the widened base of a foundation that spreads a column's concentrated load over a large enough area of soil that the ground can carry it safely. Without a footing, a column would punch into the earth like a heel into soft ground; the footing acts like a snowshoe, distributing the load.
The most common type in house construction is the isolated (pad) footing — a square or rectangular RCC slab under each column. Other types include combined footings (under two close columns), strip footings (under walls) and raft footings (a single slab under the whole building, used on weak soil).
Footing size is governed by the column load and the soil's safe bearing capacity: required area = load ÷ bearing capacity. A weaker soil needs a larger footing for the same load. Footings use a lower steel density than columns (around 60 kg/m³). Sizing a footing is a structural-engineering task — it must account for factored loads, punching shear and reinforcement, not just the bearing area.