I’ve heard about this practice when you want to have more security or multi-platform soft, you need that something between client and server to handle request properly. For example no need to create database handlers on your mobile app and site, just send the same request to your something, what will deal with database and create JSON (whatever type you wanna get on your client) from SQL types.

I was thinking it may be called web application since the connection mostly happenning through Internet these days. But Wikipedia says access happens using web browser which is not really the case, it happens using http-requests… So how can I call it?