What is eccentric loading to columns and when will it occur?

If load is not being transferred on center-lines of columns all the loads may consider as eccentric loads or in other case, when framing of a structure is such as beams are off-center from columns and un-symmetrical panels / loading is there than for sure eccentric loading will be occurred.

Eccentric loading to columns appear generally in the edge of the structure columns. It is the combination of a normal effort and a moment of bending.