HostBuilder.Build doc: mention lifetime

src/libraries/Microsoft.Extensions.Hosting.Abstractions/src/BackgroundService.cs

@@ -29,6 +29,7 @@ public abstract class BackgroundService : IHostedService, IDisposable
         /// </summary>
         /// <param name="stoppingToken">Triggered when <see cref="IHostedService.StopAsync(CancellationToken)"/> is called.</param>
         /// <returns>A <see cref="Task"/> that represents the long running operations.</returns>
+        /// <remarks>See <see href="https://docs.microsoft.com/dotnet/core/extensions/workers">Worker Services in .NET</see> for implementation guidelines.</remarks>
         protected abstract Task ExecuteAsync(CancellationToken stoppingToken);
 
         /// <summary>

src/libraries/Microsoft.Extensions.Hosting.Abstractions/src/IHost.cs

@@ -13,12 +13,13 @@ namespace Microsoft.Extensions.Hosting
     public interface IHost : IDisposable
     {
         /// <summary>
-        /// The programs configured services.
+        /// Gets the services configured for the program (for example, using <see cref="M:HostBuilder.ConfigureServices(Action&lt;HostBuilderContext,IServiceCollection&gt;)" />).
         /// </summary>
         IServiceProvider Services { get; }
 
         /// <summary>
-        /// Start the program.
+        /// Starts the <see cref="IHostedService" /> objects configured for the program.
+        /// The application will run until interrupted or until <see cref="M:IHostApplicationLifetime.StopApplication()" /> is called.
         /// </summary>
         /// <param name="cancellationToken">Used to abort program start.</param>
         /// <returns>A <see cref="Task"/> that will be completed when the <see cref="IHost"/> starts.</returns>

src/libraries/Microsoft.Extensions.Hosting/src/HostBuilder.cs

@@ -121,6 +121,7 @@ public IHostBuilder ConfigureContainer<TContainerBuilder>(Action<HostBuilderCont
         /// Run the given actions to initialize the host. This can only be called once.
         /// </summary>
         /// <returns>An initialized <see cref="IHost"/></returns>
+        /// <remarks>Adds basic services to the host such as application lifetime, host environment, and logging.</remarks>
         public IHost Build()
         {
             if (_hostBuilt)