What is the difference between a beam and a column?
In structural engineering, we give names to different structural members based on their behavior under applied load.
Say you have a rod of length 3 m made out of steel and a load P to support.
You decide to hang the rod from the ceiling and hook the load to the other end of the rod. The load, in this case, is being transferred primarily by tension and thus we call it a Tie.
In the second case, the rod is kept vertically on the floor and the load is placed on top of it. Now the load is being transferred by compression and thus we call it a Column.
In the third case, we keep the rod on two supports and then place a load on top of it. This time the primary mode of load transfer is by bending and thus we call it a Beam.
In the fourth case, we keep the rod vertical and apply load horizontally to it. This time the primary mode of load transfer is also by bending and thus we call it a Beam.
It is important to notice here that in all the above four cases nothing physically got changed with the rod in term of its material properties, cross-section or length. The only thing that changed was the way in which the load was being transferred to it.