It's about architecture, design, and process.
We like to joke that the job of an architect is to draw rectangles and point arrows at them. Which to a certain extent it's true, that is an important step in designing complex systems. The starting point for any software development is to figure out what the software is supposed to do, who your users are, and why this is important. You will begin with this requirements gathering phase. Once you understand your software's requirements and your users, you can start laying out the overall design. In software, this is a process of decomposition, breaking the big thing, your program, into smaller manageable units that you can start programming. In a modern cloud-based system, it is considered a best practice to break your application into microservices.
Microservices refers to an architectural style for developing applications. Microservices allow a large application to be decomposed into independent constituent parts, with each part having its own area of responsibility.
To serve a single user or API request, a microservices based application can call many internal microservices to compose its response. This has a significant effect on the agility of the application in aspects such as development speed, deployment, and monitoring.