The "d subshell" is a type of atomic orbital found in the electron configuration of elements. It can hold a maximum of 10 electrons and consists of five distinct orbitals, each capable of accommodating two electrons. The d subshell is important for the chemical properties of transition metals, which are found in the d-block of the periodic table. In terms of energy levels, the d subshell typically appears after the s subshell of the same principal energy level and after the s subshell of the previous energy level. This means that the 3d subshell fills after the 4s subshell, and the 4d subshell fills after the 5s subshell, influencing the arrangement of electrons in an atom.