Strutural Snaps are used by Structural elements to intelligently join them, look up "Structural Snaps" in the help documentation for more details.
By default the "Key point snap" of AECOsim Building Designer snaps to the end points of a beam axis or the center of a column, the Structural Snap icons will be displayed as the cursor approaches the keypoints. If "Key Point Snap" is active it will identify the end of the beam axis or the center of a column if you move the cursor next to the beam or column.
This is generally the desired behaviour when working with structural elements as the correct connection points are likely to be those used for placement.
However, in this example note that the wall is snapping to the centre of the column rather than the face, note the Structural Snap icon that pops up.:
In this case Structural Snaps can be toggled: