The DigiD (Digital Identification) is a way of providing secure access to national and local authority websites and to a growing number of other websites such as health insurers and pension funds.
The DigiD is linked to the BSN (issued upon registration at the municipality). Only Dutch nationals are able to apply for a DigiD when not resident in the Netherlands.
Application for a DigiD can be done via their website (in Dutch). Applicants will be prompted to choose a gebruikersnaam (username) and wachtwoord (password), and then these two codes are subsequently used to gain access to relevant websites.
It may be useful to activate the DigiD app function at the same time, as this is becoming required more often.