Unify Fallback

docs/strategies/fallback.md

@@ -2,12 +2,19 @@
 
 ## About
 
-- **Options**: [`FallbackStrategyOptions<T>`](xref:Polly.Fallback.FallbackStrategyOptions`1)
-- **Extensions**: `AddFallback`
-- **Strategy Type**: Reactive
+- **Option(s)**:
+  - [`FallbackStrategyOptions<T>`](xref:Polly.Fallback.FallbackStrategyOptions`1)
+- **Extension(s)**:
+  - `AddFallback`
+- **Exception(s)**: -
 
 ---
 
+The fallback **reactive** resilience strategy provides a substitute if the execution of the callback fails. Failure can be either an `Exception` or a result object indicating unsuccessful processing. Typically this strategy is used as a last resort, meaning that if all other strategies failed to overcome the transient failure you could still provide a fallback value to the caller.
+
+> [!NOTE]
+> In this document the *fallback*, *substitute*, and *surrogate* terms are used interchangeably.
+
 ## Usage
 
 <!-- snippet: fallback -->
@@ -59,11 +66,12 @@ new ResiliencePipelineBuilder<UserAvatar>().AddFallback(optionsOnFallback);
 
 ## Defaults
 
-| Property         | Default Value                                                              | Description                                                                                 |
-| ---------------- | -------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------- |
-| `ShouldHandle`   | Predicate that handles all exceptions except `OperationCanceledException`. | Predicate that determines what results and exceptions are handled by the fallback strategy. |
-| `FallbackAction` | `Null`, **Required**                                                       | Fallback action to be executed.                                                             |
-| `OnFallback`     | `null`                                                                     | Event that is raised when fallback happens.                                                 |
+| Property       | Default Value                                           | Description                                                                                           |
+|----------------|---------------------------------------------------------|-------------------------------------------------------------------------------------------------------|
+| `ShouldHandle` | Any exceptions other than `OperationCanceledException`. | Defines a predicate to determine what results and/or exceptions are handled by the fallback strategy. |
+
+| `FallbackAction` | `Null`, **Required**                                                       | This delegate allows you to **dynamically** calculate the surrogate value by utilizing information that is only available at runtime (like the outcome).                                                             |
+| `OnFallback`     | `null`                                                                     | If provided then it will be invoked before the strategy calculates the fallback value.                                                 |
 
 ## Diagrams
 

docs/strategies/retry.md

@@ -11,7 +11,7 @@
 
 ---
 
-The retry **reactive** resilience strategy re-executes the same callback method if its execution fails. Failure can be an `Exception` or a result object indicating unsuccessful processing. Between the retry attempts the retry strategy waits a specified amount of time. You have fine-grained control over how to calculate the next delay. The retry strategy stops invoking the same callback when it reaches the maximum allowed number of retry attempts or an unhandled exception is thrown / result object indicating a failure is returned.
+The retry **reactive** resilience strategy re-executes the same callback method if its execution fails. Failure can be either an `Exception` or a result object indicating unsuccessful processing. Between the retry attempts the retry strategy waits a specified amount of time. You have fine-grained control over how to calculate the next delay. The retry strategy stops invoking the same callback when it reaches the maximum allowed number of retry attempts or an unhandled exception is thrown / result object indicating a failure is returned.
 
 ## Usage