I have salesforce communities for customers. We have some external existing apps built on some other technology. What I am looking for exactly is how our customers can login to those external apps directly from salesforce.
I have googled and found that this can be done using OAuth or something but still not having the clear idea how to work out this.
Let's say, the customer is already logged in communities and they want to use the external app. There will some link or button which will redirect them to that app home page. This should be done in a way that the customer doesn't have to provide login credentials again. The external app should check that if the customer is logged in salesforce and if so then allow them to use the external app.
Appreciate if someone provides the solution in detail or layman's language.