A microservice is a method used to develop a scalable software system that will support any kind of device. It is an easily and independently deployable modular service that will run a unique process, and communicates through a lightweight mechanism to fulfill business requirements.
To understand microservices architecture, you need to understand what a monolithic architecture style is and why we need microservices. In a monolithic architecture, an application is created with tightly coupled modules as single units and is deployed on the web or an application. If you want to modify or scale the application, then you need to build and deploy an entire application or scale the whole application, instead of specific components. In this case, microservices can help you.
The following diagram shows the difference between monolithic and microservices architecture:
