Hi subbaiah yeti ,

• Okta Identity Engine is the platform update to Okta’s authentication services. Instead of relying on predefined behavior for identification, authorization, and enrollment, Identity Engine offers customizable building blocks that can support dynamic, app-based user journeys.
• Okta Access Gateway is a reverse proxy based virtual application, designed to secure web applications that don't natively support SAML or OID. It can be seamlessly integrate your legacy web based applications with Okta’s Cloud Single Sign-On (SSO) and Adaptive Multi-Factor Authentication (MFA) services. Since it is deployed behind the firewall, it lets external users access on-premises web-based applications without the need for traditional VPNs.