In previous versions of Drupal, entity hooks for load, update, delete, etc. were invoked in an ad-hoc manner by individual entity type modules (node, user, etc.).
In Drupal 8, most entity hooks have been unified, and they are invoked from the entity storage controller classes.
So, the documentation of these entity hooks has also been unified. The old entity hooks are still invoked, but they are not documented separately.
For instance, in Drupal 7, there was documentation for hook_entity_insert(), hook_comment_insert(), hook_user_insert() etc.
In Drupal 8, there is instead just documentation for hook_ENTITY_TYPE_insert(), which is invoked for node, user, comment, and other entity types.
There are no code changes needed in modules that implement these hooks, but if you are looking for hook documentation, you will need to search for using the new names. The new hook documentation is in file core/modules/system/entity.api.php.
Hooks whose documentation has been consolidated in this way:
hook_comment_create()
hook_comment_delete()
hook_comment_insert()
hook_comment_load()
hook_comment_predelete()
hook_comment_presave()
hook_comment_update()
hook_comment_view()
hook_comment_view_alter()
hook_file_create()
hook_file_delete()
hook_file_insert()
hook_file_load()
hook_file_predelete()
hook_file_presave()
hook_file_update()
hook_menu_delete()
hook_menu_insert()
hook_menu_update()
hook_menu_link_delete()
hook_menu_link_insert()
hook_menu_link_load()
hook_menu_link_presave()
hook_menu_link_update()
hook_node_create()
hook_node_delete()
hook_node_insert()
hook_node_load()
hook_node_predelete()
hook_node_presave()
hook_node_revision_delete()
hook_node_update()
hook_node_view()
hook_node_view_alter()
hook_node_type_delete()
hook_node_type_insert()
hook_node_type_update()
hook_taxonomy_term_create()
hook_taxonomy_term_delete()
hook_taxonomy_term_insert()
hook_taxonomy_term_load()
hook_taxonomy_term_predelete()
hook_taxonomy_term_presave()
hook_taxonomy_term_update()
hook_taxonomy_term_view()
hook_taxonomy_term_view_alter()
hook_taxonomy_vocabulary_create()
hook_taxonomy_vocabulary_delete()
hook_taxonomy_vocabulary_insert()
hook_taxonomy_vocabulary_load()
hook_taxonomy_vocabulary_predelete()
hook_taxonomy_vocabulary_presave()
hook_taxonomy_vocabulary_update()
hook_tour_insert()
hook_tour_load()
hook_tour_presave()
hook_tour_update()
hook_user_create()
hook_user_delete()
hook_user_insert()
hook_user_load()
hook_user_predelete()
hook_user_presave()
hook_user_update()
hook_user_view()
hook_user_view_alter()
hook_user_role_delete()
hook_user_role_insert()
hook_user_role_presave()
hook_user_role_update()
