RESTFul APIs provide a simple and standardized way for the microservices to exchange data, making them a common choice for implementing inter-service communication in microservices. By exposing the APIs as endpoints, it is possible for the microservices to communicate with each other using a common protocol, such as HTTP, which is widely supported and well understood. 

https://learn.microsoft.com/en-us/azure/architecture/microservices/design/interservice-communication