service-network: add some clarity to headless service

Author: binchenX

content/en/docs/concepts/services-networking/service.md

@@ -458,7 +458,7 @@ selectors defined:
 
 For headless Services that define selectors, the endpoints controller creates
 `Endpoints` records in the API, and modifies the DNS configuration to return
-records (addresses) that point directly to the `Pods` backing the `Service`.
+A records (IP addresses) that point directly to the `Pods` backing the `Service`.
 
 ### Without selectors