@supply-geoscientist1 Warm welcome to the community
You can check more on Postman official link.
Postman is a platform to build, test, design, modify, and document APIs. It is a simple Graphic User Interface for sending and viewing HTTP requests and responses.
I believe you are new to API’s and API Testing part. No worries, there is lot of documents/videos online to explain more about it. I have written a small article and published my API Testing tutorial document here. This would just be a start, you would need to learn more about Rest API architecture and jargons since you mentioned you need to handle about Rest API’s.
Coming to your real question, you have mentioned that you need to connect two applications. Can you explain a bit more here? I understand that you are a newbie here But please try to provide more details as much as possible.
So check with the developers if they have something called the API documentation. And this is where you get to know more about your API capabilities. Any application if they have an API developed for it, you can try hitting them through Postman. Simple as submitting a request on behalf of an application (Client), using another application’s API (Server), and checking that it returns the expected response.
Few other useful links for you: