Technology changes in rapid phases. It's hard to keep up with everything unless you know fundamentals, yeah. Increase in application interfaces such as desktop, mobile, api, vr, ar, audios and microservices had a huge impact in the way applications were developed. The modern startups should implement best practices to serve the future.

The platforms:

Coupled - product grows vertically/stacked
Standalone applications like microsoft office, adobe photoshop  and other offline apps have only one user interface like desktop applications. These applications have a common code base developed in version controlled fashion and get updated via the internet or patches (i.e. offline update).

Decoupled - product grows horizontally/loosely packed
Rapid adoption of mobiles, tablets and media have significantly increased application service consumptions in various interfaces. Development Practices shifted towards functional based programming i.e. each computer task is split into multiple small individual units/tasks so separate code base with their own versions controlled environment.

The Split

Frontend - mobile view, desktop view, mobile application interface(buttons, list etc).

Backend - serves multiple frontend/UI with centralized DB, files, processing etc.

Api - device to devices communication which doest need visible frontend for interaction eg: server to server data transfers.

Microservices - sub task which is able do particular task well like video processing, audio/image processing, Artificial intelligence etc in both front and backend and api’s.

Bonus:
Distributed computing has skyrocketed due to an increase in the amount of data generated i.e. single task processed by multiple systems.