S-orbitals are a type of atomic orbital that can hold a maximum of two electrons. They are spherical in shape and are found in every energy level of an atom, starting from the first level. The first energy level has one s-orbital, while higher energy levels have one s-orbital each as well. In the context of quantum mechanics, s-orbitals are described by the quantum number l equal to 0. This means they have no angular momentum, making them simpler than other types of orbitals, such as p-orbitals or d-orbitals. S-orbitals play a crucial role in the electron configuration of elements in the periodic table.