Abstract: Rare-earth elements, characterized by partially filled 4f shells, can typically form trivalent ions when doped into inorganic crystals. These ions exhibit inhomogeneously broadened 4f-4f transitions in the visible and near-infrared spectral ranges, with optical coherence lifetime up to millisecond level, making them an ideal platform for constructing quantum interfaces. Erbium ions, in particular, possess stable optical transitions within the 1530 nm~1565 nm wavelength range, which perfectly aligns with the operational band of existing fiber-optic communication networks. Owing to this compatibility, erbium ions are garnering increasing attention in quantum information technologies. This review begins with an overview of the luminescent properties of erbium ions, followed by recent advances in single-photon emission from individual erbium ion enhanced by optical microcavities, methods for addressing individual ions via distinct emission wavelengths, and optical-atomic interfaces utilizing single erbium ion.