Loads refer to the forces acting on a structure employed in the design process to verify its strength and stability. They can include dead loads (e.g. self weight), live loads (e.g. people), wind loads, seismic loads, snow loads, and others.
The seismic load on a structural model can be included either as a set of static horizontal/vertical forces or, alternatively, as dynamic excitation, in the form of an accelerogram applied to external constraints.