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 levels can have multiple s-orbitals. In the context of the quantum mechanical model of the atom, s-orbitals are important for understanding how electrons are arranged around the nucleus. They play a key role in determining the chemical properties of elements, as they are involved in bonding and interactions with other atoms.