Does "FrontEnd <-> BackEnd <-> Backend2" exist?

Question

Could someone please explain the difference between server-side of a website and a backend? I'm working in IT company, we do have several websites. They are being controlled by API's written in C# in our environment and our databases.
However. there are some external DBs used: to get data from third-parties to our DB using Java Backend API's

So is it like "real" BackEnd (Java) -> Our BackEnd (C#)-> FrontEnd?

Answer 1

You can think of each API (the web service part of your webapp) as a back end (including the one that hooks into the database). You are not limited to one API, and you can build all or some of them yourself (or hook into vendor APIs), but collectively they are known as the back end (i.e. server-side).

Front end is client-side (HTML, CSS, JavaScript, and any related frameworks and libraries). It's the UI or website part of your webapp.

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