JWT and the JOSE Family
JSON Web Token (JWT) is a compact, URL-safe token format used for authentication and stateless authorization. JWT is the most-used member of the JOSE family (JavaScript Object Signing and Encryption): JWS, JWE, JWK, JWA. Most “JWTs” you’ll see are signed (JWS); encrypted (JWE) is rarer.
For security pitfalls (the most-tested angle), see JWT pitfalls. For SSO and OIDC context: SSO — Deep Topical Notes and OAuth 2.0 and OpenID Connect.