A column is a vertical structural member designed to transfer a compressive load. For example, a column might transfer loads from a ceiling, floor or roof slab or from a beam, to the foundations.
Columns also carry the bending moment about one or both axes of their cross-section.
Biaxial bending affects columns where the load is eccentric about both the axes in the plane of the column (eccentric load is a force placed upon a portion of a column which is not symmetric with its central axis, thereby producing bending).
For both rectangular and square columns, there are situations in which axial compression is accompanied by simultaneous bending about both principal axes of the section.