When to consume webservice and when to expose web service in SAP ABAP?

Hi Team,

I'm new to webservices , want to understand when to consume and expose a web service?

i understood from a video that we can generate a web service with the RFC in sap and generate the WSDL file and when we give this WSDL file to any front end system they can consume our web serive and RFC data.

But i'm confused in some video they are showing how to consume the web service in SAP ABAP , like going into SE80 , package , service name etc....

Is web service is used only to expose the SAP DATA via RFC web service to front end systems ?

or we can also consume other front end web services into our SAP ? , if so why we will consume into SAP ?

Can you please explain when we will use these web services expos and consume in real time in a lay man laguage.

Thanks,

Priya.