Add hostname descriptions

Fixes #3818

docs/setup/network.md

@@ -17,19 +17,20 @@ A handful of features within VS Code require network communication to work, such
 
 If you are behind a firewall that needs to allow specific domains used by VS Code, here's the list of hostnames you should allow communication to go through:
 
-* `update.code.visualstudio.com`
-* `code.visualstudio.com`
-* `go.microsoft.com`
-* `vscode.blob.core.windows.net`
-* `marketplace.visualstudio.com`
-* `*.gallery.vsassets.io`
-* `*.gallerycdn.vsassets.io`
-* `rink.hockeyapp.net`
-* `vscode.search.windows.net`
-* `raw.githubusercontent.com`
-* `vsmarketplacebadge.apphb.com`
-* `az764295.vo.msecnd.net`
-* `download.visualstudio.microsoft.com`
+* `update.code.visualstudio.com` - Visual Studio Code download and update server
+* `code.visualstudio.com` - Visual Studio Code documentation
+* `go.microsoft.com` - Microsoft link forwarding service
+* `vscode.blob.core.windows.net` - Visual Studio Code blob storage, used for remote server
+* `marketplace.visualstudio.com` - Visual Studio Marketplace
+* `*.gallery.vsassets.io` - Visual Studio Marketplace
+* `*.gallerycdn.vsassets.io` - Visual Studio Marketplace
+* `rink.hockeyapp.net` - Crash reporting service
+* `bingsettingssearch.trafficmanager.net` - In-product settings search
+* `vscode.search.windows.net` - In-product settings search
+* `raw.githubusercontent.com` - GitHub repository raw file access
+* `vsmarketplacebadge.apphb.com` - Visual Studio Marketplace badge service
+* `az764295.vo.msecnd.net` - Visual Studio Code download CDN
+* `download.visualstudio.microsoft.com` - Visual Studio download server, provides dependencies for some VS Code extensions (C++, C#)
 
 ## Proxy server support