What a web service is
In the course of your work as an analyst, you may need to retrieve data through an API, exposed by a system within your network, for example. However, this is a rare case, since today almost all external data sources are exposed as web services, even within a company.
Web services are the most common and popular way of communicating information between heterogeneous information systems. A web service is basically a software module hosted on a server that is available over the internet to provide data to specific requests from a client.
There are mostly two types of design models for web services: Simple Object Access Protocol (SOAP) and REpresentational State Transfer (REST):