The document discusses APIs, defining them as interfaces that allow applications to communicate and share data over a network. It notes that APIs act as an interface between clients and servers, exposing backend data through operations, inputs, outputs, and data types. The document also outlines the benefits of APIs in standardizing communication and enabling reusability. It introduces common API terminology and types, focusing on web APIs which are the most widely used.

1. The most talkative topic across the word, three letter words the API.

2.  What is an API
 Few words about API
 Advantages of API
 Standard terminologies used with API
 Types of APIs
 Introducing different types of WEB APIs

3. API Definition:
API stands for Application Programming Interface. API can be
defined in many ways. And its definitions varied from one
context to another. The best possible way to define an API is as
follows:
 API stands for Application Programming Interface. It acts as
the interface in between client & server which is used to
provide communication or interaction over network via
HTTP/HTTPs Protocol which help us to expose the data or
information from the backend systems.

4. API Diagram:
Client Applications Server Applications
Client 1
Client 2
Client n
API
SFDC

5.  API is used to merge or integrate the data from different backend systems or
applications or devices all together in the integration based project environment
and then acts as an interface(single face) or Single Point of Contact (SPOC) to the
multiple clients. So that later on client can make a call or request to an API by
using some standard tools such as Postman or cURL or by doing coding to
consume or orchestrate an API to expose the data or information present in an API
based on URI type (resource type in case of REST API).
 API is used to store the data from different applications in integration project.
 API acts as an interface which is used to expose or access the data from the
backend applications by using operations, Input, Output and underlying Data
types.

6.  APIs acts as an interface to allow applications to talk to each
other. It provides information for how to communicate with
an applications by defining the :
Operations (methods)
Inputs (request )
Outputs (response)
Underlying data types
 API is sometimes also referred as Web Services, Endpoints.

7.  API is built or created by the Service provider which is used to
perform some functionality. It is actually used to stores data
from different backend systems. Old days gone when we used
to depend on point to point interaction. Now API is used to
expose the data from backend systems. Service consumer or
client uses APIs to expose data from multiple backend
applications based on operation & resources.
 API is built by the service provider and then it is deployed to
the Cloud computing environment so that it will be available
for everyone. From there multiple clients can consume or
orchestrate our APIs based on operation and resources which
is hosted in the Cloud computing environment.

8.  API is used in Integration based project. The example of other
integration technologies are JDBC which is used to expose or
access the data or information from the database in the form of
operations (Java methods). If client wants they can make a call or
request to the specific methods to get the data back. But this will
happen from server to server only.
Hibernate, iBatis are also one type of integration technology
only.
 All the service or business components or class in MVC pattern
are type of integration technology.
 EJB & WS are another type of integration technology. A WEB APIs.
 We can create Web API or Web Services by using basically three
technologies:
1> SOAP API 2> RPC API and 3> RESTful API

9. There are various benefits of API. Few of them I would like to highlight it
out here.
Benefits of API:
 Standard Interface for communications:
It is a standard way of communication in between client & server.
 Provide Abstraction:
It provides Abstraction in between Client & Server.
 Reusability (Easy to use):
It supports Reusability . Multiple clients can consume an APIs once created
by the service provider.

10. To understand about the API we have to understand some standard terminologies
which is used with APIs. So these are the following standard terminologies often
used in APIs….
 Client:
One who is responsible for consuming our APIs. It might be more than one. Or
One who sends requests to APIs or make a call to consume an API. (Many clients
can consume our API)
 Server:
One who is responsible for providing services to the clients by making API. One
who is responsible to creating an API and sending a response to the API request

11.  Stateless:
Communication happens in between applications over standard
HTTP / HTTPS protocol which is stateless.
 Resources/Categories/Entities:
Resources is nothing but a URI basically which is used to send a
request to consume or make a call/request to an API by the client to
expose or get the data from the API back to the client based on
resource type defined in an API.
Resources are Entities or Categories that has a URI to which request
can be sent.
Resources are derived from the Categories.
Resources are Noun & Methods are Verbs..
BY using Resources only we can expose the data from the backend
applications.
Resources are sometimes referred as Operations as well

12.  Methods/Operations/Actions:
It is a standard HTTP method which is used by the clients to make a
request or call to an API to expose data.

13. Types of APIs:
There are basically two types of APIs
1. Traditional APIs
2. Web APIs (Advanced one) This one is more famous now
Traditional API:
This type of API is very old type API. It is basically used in server to
server, libraries which is available in source code file to expose
data.
WEB API:
This type of API is most advanced one and used in IT industry so
frequently to expose data from backend systems across network
via standard protocols like HTTP/HTTPs.

14.  There are more than ten thousands Public WEB APIs are
available which helps to connect different applications via
internet exists.
 Web APIs are created in web formats & standards.
 SOAP APIs, RPC APIs and REST APIs are the examples of WEB
APIs..
 JSON-RPC APIs & XML-RPC APIs are the examples of RPC Web
Service or APIs