Intealth is a nonprofit organization that brings together ECFMG (the Educational Commission for Foreign Medical Graduates) and FAIMER (the Foundation for Advancement of International Medical Education and Research). Its name appears in "ECFMG | Intealth" on official pages.
For IMGs, the most visible part is MyIntealth, the online portal used to apply for ECFMG Certification, upload credentials, verify identity and request an ERAS token. The World Directory of Medical Schools, which determines whether your school is eligible, is part of the same family of services.
ECFMG remains the name of the certification program. See the MyIntealth account guide and the World Directory guide.