Entity

Using entity_load function.

Example:
$entity = entity_load($entity_type, $id);

Using Entity Manager

Example:
$entity = \Drupal::entityTypeManager()->getStorage($entity_type)->load($id);

Get entity types list :

$itmes_list= \Drupal::entityTypeManager()->getDefinitions();

Get Entity type (Content / Config)

$itmes_list['node']->getGroup();
$itmes_list['node_type']->getGroup();

Once created your entity as Basic Entity or Full Entity, you can add a custom views handler.

This is a full Example of the Entity 'Vehicle' with user interfaces for:
- Actions (Create, Edit, Delete)
- Listing builder
- Entity settings pages
   - Manage fields
   - Manage form display
   - Manage display

Drupal 8 has two type of entities, ContentEntity and ConfigEntity. Content entity is based on database table and config entity is based on Drupal config table.

Add a new field:

Example 1 Automatic update:

1. Update baseFieldDefinitions() of the Entity.
2. Apply update from a mymodule_update_N(). Ex: