Magnetostatics is the theory of the magnetic field in conditions in which its behavior is independent of electric fields, including
The magnetic field associated with various spatial distributions of steady current
The energy associated with the magnetic field
Inductance, which is the ability of a structure to store energy in a magnetic field
The word ending “-statics” refers to the fact that these aspects of electromagnetic theory can be developed by assuming that the sources of the magnetic field are time-invariant; we might say that magnetostatics is the study of the magnetic field at DC. However, many aspects of magnetostatics are applicable at “AC” as well.