In order to create an entity in Drupal 8 in a general case we need to Entity type manager to get a storage for a specific entity type, for example node 

// Use the entity manager to get node storage.
$node_storage = \Drupal::entityTypeManager()->getStorage('node');

// Call create method passing values for a new node entity.
$node_storage->create([
   'type' => 'page', 
   'title' => 'Page title',
]);

Or we can write it shorter

$node = \Drupal::entityTypeManager()->getStorage('node')->create(['type' => 'page', 'title' => 'Page title']);

We can also call a wrapper - a function, which provides the same functionality. I don't recommend to use it, because it is deprecated and  can be removed at any moment

$node = entity_create('node', [
  'type' => 'page',
  'title' => 'Page title',
  'body' => 'This a text of your page.',
]);

We can also call directly call method create of a specific entity

$node = Node::create([
  'type' => 'page',
  'title' => 'The page title',
]);