Footing is a part of a structure to distribute load safely to foundation. The foundation is the lowest part of the structure. Examples of footing are trip footing, combined footing and spread footing. Sometimes when the bearing capacity is low we have to construct a foundation which becomes part of the structure. For example mat foundation or well foundation.
In summary, the structure or part which helps to transmit the load from upper stories through columns up to the ground, is called footing. Every column in the structure has to have a footing supported on firm and hard strata. As there may be many numbers of columns, so can be footings. The overall arrangement of footings are interconnected with beams and all which ultimately distributes the loads safely to the ground, can be called a foundation.