Structural Engineering is a field of analytic thinking and designing of structures to oppose the resisting loads it is subjected to carry. It is a specialty of doctorate and mastery in the Civil Engineering field.
Structural Engineers are engage to designing vertical and horizontal structures like buildings, skyscrapers, subways and bridges, etc.
The need to satisfy the design criteria for a certain structure is a must and hence it approves the structural integrity in a certain level. This field of engineering is based and is always evolving in the physical laws of the materials of the structure, landscape and climate. By following criteria, the engineer can calculate the years of serviceability of a structure, its performance against earthquake, natural disasters and wind/snow load and its safety for occupancy. It is the Structural Engineer's responsibility to make effective structures that is equally cost efficient.
Hence, one can say, "I didn't just build it, I engineered it!"