Data integration between Oracle and an external application?

We have an application that requires certain HR (Human Resource) data such as employee table, etc. to initiate a guide and automate the workflow process for which it is used.

Well I'm looking into a way to integrate or sync with Oracle Data, say I get a new customer who has something called "Oracle HR" and they say we will buy your application, but we need you to integrate it with our Oracle HR System.

Our application is in .NET C #. How can I integrate with Oracle?

1. Are there web services in oracle that provide data that I can poll and get and put into my database applications?

1. Or should I ask them to provide I am a user who can access the data like so that I can connect via ADO.NET or any other adapter and get the data?

2. What the hell is Oracle Fusion Secondary software in a layman developer's timing? Can it be used or is it advertising?

Anyone with some experience in this area of ​​two-way or one-way data integration in an enterprise can shed some light? Thanks in advance.