There are two basic messaging patterns for communication between two microservices:
In this pattern, a service calls an API that another service exposes, using a protocol such as HTTP or gRPC. This option is a synchronous messaging pattern because the caller waits for a response from the receiver.
In this pattern, a service sends message without waiting for a response, and one or more services process the message asynchronously. This is done by using a message broker or event bus.
Further information check out https://docs.microsoft.com/en-us/azure/architecture/microservices/design/interservice-communication