Single sign-on
Also known as SSO
Signing in once to an identity provider and reaching many applications without authenticating again to each.
SSO reduces password sprawl and gives you one place to enforce MFA, apply conditional access, and cut off a departing employee. Without it, offboarding means hunting through dozens of applications and hoping you found them all.
It also concentrates risk, since compromise of the identity provider reaches everything behind it. That concentration is a good trade, but only if the identity provider itself is protected accordingly.
Where this comes up
Single sign-on sits inside our identity and access work. If you are trying to work out what this means for your own environment rather than in the abstract, that is the page worth reading next, and a short call will get you a straight answer faster than either.