In plain English
SSO lets your staff log in to their computer once — or authenticate through Microsoft Entra ID — and access all connected applications (email, CRM, cloud storage, HR systems) without entering separate passwords for each. This improves productivity and, when combined with MFA, can actually reduce security risk compared to managing dozens of separate passwords.
Full definition
SSO removes the need for a separate username and password for every application. A user authenticates once through a central identity provider, and that authentication is trusted across connected systems for the duration of the session. In environments, (formerly Azure Active Directory) acts as that identity provider. It issues a token after login, and applications that trust Entra ID accept that token instead of prompting the user to log in again.
The security benefit is less obvious than it first appears. Fewer passwords means fewer weak or reused ones, which reduces exposure to credential stuffing. It also means IT can cut access to every connected application by disabling a single account, which matters when you need to offboard a departing employee quickly. If your HR process takes a week to remove someone from a dozen separate systems, SSO with a single disable action closes that window.
SSO does concentrate risk. If the identity provider account is compromised, an attacker has access to everything that trusts it. This is why SSO should always be paired with on the central login. A stolen password alone should not be enough to get through. With MFA on the Entra ID account and blocking logins from unexpected locations or devices, SSO becomes a security improvement rather than a single point of failure.