Update README.md

README.md

@@ -1,5 +1,13 @@
 # Apache SkyWalking data collect protocol
-Apache SkyWalking can collect data from different sources. Each kind of source should follow the protocols in this repo.
+Apache SkyWalking typically collect data from 
+1. Language agent, including Java, .Net, PHP, Golang, NodeJS, Lua.
+1. Service mesh proxy, especially Envoy controlled by Istio
+1. 3rd libs, such as Zipkin, Jaeger
+
+This repo hosts the protocol of SkyWalking native report protocol, defined in gRPC. Read [Protocol DOC](https://github.com/apache/skywalking/blob/master/docs/en/protocols/README.md#probe-protocols) for more details
+
+## Release
+This repo wouldn't release separately. All source codes have been included in the main repo release. The tags match the [main repo](https://github.com/apache/skywalking) tags.
 
 ## License
 Apache 2.0