Archana puja is a brief intercessionary puja on behalf of an individual that can be undertaken after the main puja.
The purpose of Archana is to thank god for giving us all what we need for survival – be it the strength to endure agony or the basic essentials.
It is indeed a thanksgiving gesture that cultivates the habit of sharing and caring. The Prasad offered to the deity is distributed among people and thus the fruits of prayers reach the needy too.