The TIE (Tarjeta de Identidad de Extranjero) is the physical document that certifies the legal residence status of a non-EU foreign citizen in Spain. It is issued by the Dirección General de la Policía and contains your photo, address, NIE number, type of authorisation and validity dates.
You need it if you have been granted authorisation to reside in Spain for more than six months: residence and work permit, studies, family reunification, arraigo, digital nomad visa or non-lucrative residence. It is your identity document within Spanish territory.