diff --git a/core/modules/media/src/MediaHandlerInterface.php b/core/modules/media/src/MediaHandlerInterface.php
index 31dc02c6c8..4afafce5c9 100644
--- a/core/modules/media/src/MediaHandlerInterface.php
+++ b/core/modules/media/src/MediaHandlerInterface.php
@@ -9,9 +9,26 @@
 /**
  * Defines the interface for media handler plugins.
  *
+ * Media handlers are the essential part of the media entity type as they
+ * implement the knowledge and business logic related to a given sort of media.
+ * Media entity doesn't have any knowledge anything about media it represents
+ * without handlers.
+ *
+ * Each Media type needs exactly one handler and a single handler can be used on
+ * many media types.
+ *
+ * Their main responsibilities are:
+ * - defining how media is represented (stored),
+ * - providing thumbnails,
+ * - validating media before it is saved,
+ * - providing default value for the media name field,
+ * - providing metadata specific to the given media,
+ * - handling mapping between metadata and entity fields.
+ *
  * @see \Drupal\media\Annotation\MediaHandler
  * @see \Drupal\media\MediaHandlerBase
  * @see \Drupal\media\MediaHandlerManager
+ * @see \Drupal\media\MediaTypeInterface
  * @see plugin_api
  */
 interface MediaHandlerInterface extends PluginInspectionInterface, ConfigurablePluginInterface, PluginFormInterface {
diff --git a/core/modules/media/src/MediaTypeInterface.php b/core/modules/media/src/MediaTypeInterface.php
index 72429d38c7..311d0f4e70 100644
--- a/core/modules/media/src/MediaTypeInterface.php
+++ b/core/modules/media/src/MediaTypeInterface.php
@@ -8,6 +8,17 @@
 
 /**
  * Provides an interface defining a media type entity.
+ *
+ * Media types are bundles for the media entity. They are used to group media
+ * with same semantics. Media types are not about where media comes from. They
+ * are about the meaning that media has in context of a given Drupal site.
+ *
+ * Media handlers, on the other hand, are aware where media comes from and know
+ * how to represent and handle it in Drupal's context. They are aware of the low
+ * level details, while types don't care about them at all. That said, media
+ * types can not exist without handlers.
+ *
+ * @see \Drupal\media\MediaHandlerInterface
  */
 interface MediaTypeInterface extends ConfigEntityInterface, EntityDescriptionInterface, RevisionableEntityBundleInterface {