Overview of Events
Oracle Cloud Infrastructure Events enables you to create automation based on the state changes of resources throughout your tenancy. Use Events to allow your development teams to automatically respond when a resource changes its state.
Event Rules must also specify an action to trigger when the filter finds a matching event. Actions are responses you define for event matches. You set up select Oracle Cloud Infrastructure services that the Events service has established as actions. The resources for these services act as destinations for matching events. When the filter in the rule finds a match, the Events service delivers the matching event to one or more of the destinations you identified in the rule. The destination service that receives the event then processes the event in whatever manner you defined. This delivery provides the automation in your environment.
You can only deliver events to certain Oracle Cloud Infrastructure services with a rule. Use the following services to create actions:
Notifications
Streaming
Functions

References:
https://docs.cloud.oracle.com/en-us/iaas/Content/Events/Concepts/eventsoverview.htm

Serverless computing refers to a concept in which the user does not need to manage any server infrastructure at all. The user does not run any servers, but instead deploys the application code to a service provider's platform. The application logic is executed, scaled, and billed on demand, without any costs to the user when the application is idle.
Benefits of the Serverless or FaaS
So far almost every aspect of Serverless or FaaS is discussed in a brief, so let's talk about the pros and cons of using Serverless or FaaS Reduced operational and development cost Serverless or FaaS offers less operational and development cost as it encourages to use third-party services like Auth, Database and etc.
Scaling
Horizontal scaling in Serverless or FaaS is completely automatic, elastic and managed by FaaS provider. If your application needs more requests to be processed in parallel the provider will take of that without you providing any additional configuration.
References:
https://medium.com/@avishwakarma/serverless-or-faas-a-deep-dive-e67908ca69d5
https://qvik.com/news/serverless-faas-computing-costs/
https://pages.awscloud.com/rs/112-TZM-766/images/PTNR_gsc-serverless-ebook_Feb-2019.pdf

Service Choreography
Service choreography is a global description of the participating services, which is defined by exchange of messages, rules of interaction and agreements between two or more endpoints. Choreography employs a decentralized approach for service composition. the decision logic is distributed, with no centralized point.

Choreography, in contrast, does not rely on a central coordinator. and all participants in the choreography need to be aware of the business process, operations to execute, messages to exchange, and the timing of message exchanges.
References:
https://stackoverflow.com/questions/4127241/orchestration-vs-choreography/33316988

In the API Gateway service, a back end is the means by which a gateway routes requests to the back-end services that implement APIs. If you add a private endpoint back end to an API gateway, you give the API gateway access to the VCN associated with that private endpoint.
You can also grant an API gateway access to other Oracle Cloud Infrastructure services as back ends. For example, you could grant an API gateway access to Oracle Functions, so you can create and deploy an API that is backed by a serverless function.
API Gateway service to create an API gateway, you can create an API deployment to access HTTP and HTTPS URLs.
https://docs.cloud.oracle.com/en-us/iaas/Content/APIGateway/Tasks/apigatewayusinghttpbackend.htm API Gateway service to create an API gateway, you can create an API deployment that invokes serverless functions defined in Oracle Functions.
https://docs.cloud.oracle.com/en-us/iaas/Content/APIGateway/Tasks/apigatewayusingfunctionsbackend.htm API Gateway service, you can define a path to a stock response back end
https://docs.cloud.oracle.com/en-us/iaas/Content/APIGateway/Tasks/apigatewayaddingstockresponses.htm

Invoking Functions
You can invoke a function that you've deployed to Oracle Functions in different ways:
1. Using the Fn Project CLI.
2. Using the Oracle Cloud Infrastructure CLI.
3. Using the Oracle Cloud Infrastructure SDKs.
4. Making a signed HTTP request to the function's invoke endpoint. Every function has an invoke endpoint.
Using the Fn Project CLI to Invoke Functions
To invoke a function deployed to Oracle Functions using the Fn Project CLI:
Log in to your development environment as a functions developer.
In a terminal window, enter:
$ fn invoke <app-name> <function-name>
Using SDKs to Invoke Functions:
If you're writing a program to invoke a function in a language for which an Oracle Cloud Infrastructure SDK exists, Oracle recommends you use that SDK to send API requests to invoke the function. Among other things, the SDK will facilitate Oracle Cloud Infrastructure authentication.
References:
https://docs.cloud.oracle.com/en-us/iaas/Content/Functions/Tasks/functionsinvokingfunctions.htm