SAML2 based federations consist of services represented by Service Providers (SP) and Home Organizations represented by Identity Providers (IdP). Services rely on Home Organizations to identify the users and for that to happen, the services usually need to be able to direct the user to correct Home Organization. The number of Home Organizations is - particularly in eduGAIN - so vast that users have to select their Home Organization from a long list of organizations which can access a particular service. Showing this (long) list of Home Organizations requires the services to implement a so-called Identity Provider Discovery Service. Instead of operating a Discovery Service itself, an alternative solution is to rely on a Central Discovery Service, which is operated by a third party. A centrally maintained Discovery Service offers users a list of Home Organizations to pick from.
eduTEAMS Discovery service is a centrally maintained Discovery Service intended to be used by eduTEAMS services. However, there are no technical restrictions to expand the client base nor any intention to prevent non-eduTEAMS services from using it.