Update glossary and HTML meta tags

_docs/reference/glossary.md

@@ -13,14 +13,6 @@ type: markdown
 
 Service instance
 
-Service version
-
-Source - ?
-
-Destination -- a fully-qualified hostname, some tags, a Load balancing policy, a Circuit breaker policy,
-a Timeout policy, a Retry policy, a L7 fault injection policy, a L4 fault injection policy, and
-"Custom policy implementations"
-
 RouteRule - destination, MatchCondition, 0..N DestinationWeights, precedence
 
 ProxyMeshConfig -- nothing
@@ -62,6 +54,12 @@ RDS Route Discovery Service -- See https://lyft.github.io/envoy/docs/configurati
 
 # Glossary
 
+- **Destination**.
+The remote upstream service to which the proxy/sidecar is
+talking to, on behalf of the source service. There can be one or more
+service versions for a given service and
+the proxy would choose the version based on routing rules.
+
 - **Envoy**.
 Envoy is the high-performance proxy that Istio uses to mediate all inbound and outbound traffic for all services in the service mesh. 
 Learn more about Envoy [here](https://lyft.github.io/envoy/).
@@ -84,7 +82,9 @@ Mixer is an Istio component responsible for enforcing access control and usage p
 from the Envoy proxy and other services. Learn more about Mixer [here](/docs/concepts/policy-and-control/mixer.html).
 
 - **Service**.
-A well-known IP endpoint and port that implements a specific protocol.
+A unit of an application with a unique name that other services
+use to refer to the functionality being called. Service instances are
+pods/VMs/containers that implement the service.
 
 - **Service Consumer**.
 The agent that is using a service.
@@ -98,3 +98,18 @@ monitoring health via a variety of dashboards.
 
 - **Service Producer**.
 The agent that creates a service by writing source code.
+
+- **Service Versions**.
+In a continuous deployment scenario, for a given service,
+there can be multiple sets of instances running potentially different
+variants of the application binary or config. These variants are not necessarily
+different API versions. They could be iterative changes to the same service,
+deployed in different environments (prod, staging, dev, etc.). Common
+scenarios where this occurs include A/B testing, canary rollouts, etc. The
+choice of a particular version can be decided based on various criterion
+(headers, url, etc.) and/or by weights assigned to each version.  Each
+service has a default version consisting of all its instances.
+
+- **Source**.
+Downstream client (browser or another service) calling the
+proxy/sidecar (typically to reach another service).

_layouts/base.html

@@ -12,8 +12,8 @@ layout: compress
     <meta charset="utf-8">
     <meta http-equiv="X-UA-Compatible" content="IE=edge">
     <meta name="viewport" content="width=device-width, initial-scale=1">
-    <meta name="title" content="Istio">
-    <meta name="description" content="An open platform to connect, manage, and secure microservices.">
+    <meta name="title" content="{{page.title}}">
+    <meta name="description" content="{{page.overview}}">
     <title>Istio / {{ page.title }}</title>
 
     <!-- Webfont -->