grpc 引入的几个依赖都是干啥的?

比如下面这几个, 俺在网上没找到对各个依赖的说明啊~~~

        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-protobuf</artifactId>
        </dependency>

        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-stub</artifactId>
        </dependency>

        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-services</artifactId>
        </dependency>

        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-netty-shaded</artifactId>
            <scope>runtime</scope>
        </dependency>