Hi Rupesh,
Nowadays, most of websites or platforms provide developers with their API endpoint.
So what we actually need to do is send HTTP requests, but it is optional to do the integration with code or not.
There are 3 ways for Dynamics 365 to communicate with external web services.
1. Custom Workflow Activity, with C# and HttpClient class.
2. Plugin, it is similar to CWA: also with C# and HttpClient class.
Differences: CWA will create a custom step in workflow steps, we can define custom input and output parameters in .cs file code, even though the CWA is already registered to Dynamics 365, it leaves a choice for us that whether adding the step to our workflow.
Plugin: compared with limited event triggers(when a record is created/updated/deleted) of workflow, plugin can handle more messages such association and disassociation.
e.g: When we add a contact to a marketing list.
After being registered to system, plugin will always execute when the particular event comes.
3. Flow, we can call any of API endpoint using its HTTP connector.
https://d365demystified.com/2020/04/07/make-http-request-from-flow-in-power-automate/
In addition, you can create an Azure function and connect to third party system inside the function.
After publishing the whole function to Azure, register a Webhook in Plugin Registration Tool.
https://d365demystified.com/2020/03/19/call-azure-function-from-dynamics-365-crm-using-webhooks/
However, the method could still be categorized to Plugin way.
