docs: improve accessibility of toh-pt6 (#40805)

PR Close #40805

aio/content/tutorial/toh-pt6.md

@@ -9,7 +9,7 @@ Angular's `HttpClient`.
 
 <div class="alert is-helpful">
 
-  For the sample app that this page describes, see the <live-example></live-example>.
+  For the sample application that this page describes, see the <live-example></live-example>.
 
 </div>
 
@@ -17,7 +17,7 @@ Angular's `HttpClient`.
 
 `HttpClient` is Angular's mechanism for communicating with a remote server over HTTP.
 
-Make `HttpClient` available everywhere in the app in two steps. First, add it to the root `AppModule` by importing it:
+Make `HttpClient` available everywhere in the application in two steps. First, add it to the root `AppModule` by importing it:
 
 <code-example path="toh-pt6/src/app/app.module.ts" region="import-http-client" header="src/app/app.module.ts (HttpClientModule import)">
 </code-example>
@@ -33,7 +33,7 @@ Next, still in the `AppModule`, add `HttpClient` to the `imports` array:
 This tutorial sample mimics communication with a remote data server by using the
 [In-memory Web API](https://github.com/angular/angular/tree/master/packages/misc/angular-in-memory-web-api "In-memory Web API") module.
 
-After installing the module, the app will make requests to and receive responses from the `HttpClient`
+After installing the module, the application will make requests to and receive responses from the `HttpClient`
 without knowing that the *In-memory Web API* is intercepting those requests,
 applying them to an in-memory data store, and returning simulated responses.
 
@@ -127,7 +127,7 @@ Convert that method to use `HttpClient` as follows:
 Refresh the browser. The hero data should successfully load from the
 mock server.
 
-You've swapped `of()` for `http.get()` and the app keeps working without any other changes
+You've swapped `of()` for `http.get()` and the application keeps working without any other changes
 because both functions return an `Observable<Hero[]>`.
 
 ### `HttpClient` methods return one value
@@ -197,10 +197,10 @@ has configured with both the name of the operation that failed and a safe return
 </code-example>
 
 After reporting the error to the console, the handler constructs
-a user friendly message and returns a safe value to the app so the app can keep working.
+a user friendly message and returns a safe value to the application so the application can keep working.
 
 Because each service method returns a different kind of `Observable` result,
-`handleError()` takes a type parameter so it can return the safe value as the type that the app expects.
+`handleError()` takes a type parameter so it can return the safe value as the type that the application expects.
 
 ### Tap into the Observable
 
@@ -283,7 +283,7 @@ The hero now appears in the list with the changed name.
 
 ## Add a new hero
 
-To add a hero, this app only needs the hero's name. You can use an `<input>`
+To add a hero, this application only needs the hero's name. You can use an `<input>`
 element paired with an add button.
 
 Insert the following into the `HeroesComponent` template, just after
@@ -506,7 +506,7 @@ It cancels and discards previous search observables, returning only the latest s
 
   Note that canceling a previous `searchHeroes()` Observable
   doesn't actually abort a pending HTTP request.
-  Unwanted results are simply discarded before they reach your application code.
+  Unwanted results are discarded before they reach your application code.
 
 </div>
 
@@ -515,11 +515,11 @@ That's the job of the [`AsyncPipe`](#asyncpipe) in the template.
 
 #### Try it
 
-Run the app again. In the *Dashboard*, enter some text in the search box.
+Run the application again. In the *Dashboard*, enter some text in the search box.
 If you enter characters that match any existing hero names, you'll see something like this.
 
 <div class="lightbox">
-  <img src='generated/images/guide/toh/toh-hero-search.png' alt="Hero Search Component">
+  <img src='generated/images/guide/toh/toh-hero-search.gif' alt="Hero Search field with the letters 'm' and 'a' along with four search results that match the query displayed in a list beneath the search input">
 </div>
 
 ## Final code review