D-orbitals are a set of five orbitals found in the electron configuration of transition metals and some heavier elements. They are designated as dxy, dyz, dzx, dx²-y², and dz². Each d-orbital can hold a maximum of two electrons, allowing for a total of ten electrons in the d-subshell. These orbitals play a crucial role in the chemical properties and bonding of transition metals. The shape of d-orbitals is more complex than that of s and p orbitals, which contributes to their unique chemical behavior. D-orbitals are involved in various processes, including metallic bonding, catalysis, and the formation of colored compounds. Their ability to participate in bonding and electron sharing is essential for understanding the reactivity of transition metals in chemistry.