Difference between become and become_user in Ansible

Recently I started digging into Ansible and writing my own playbooks. However, I have a troubles with understanding difference between become and become_user.
As I understand it become_user is something similar to su <username>, and become means something like sudo su or “perform all commands as a sudo user”. But sometimes these two directives are mixed.

Could you explain the correct meaning of them?

become_user defines the user which is being used for privilege escalation.

become simply is a flag to either activate or deactivate the same.

Here are three examples which should make it clear:

1. This task will be executed as root, because root is the default user for privilege escalation:
   
   Default

   - do: something become: true

   1 2 3

   - do: something become: true

2. This task will be executed as user someone, because the user is explicitly set:
   
   Default

   - do: something become: true become_user: someone

   1 2 3 4

   - do: something become: true become_user: someone

3. This task will not do anything with become_user, because become is not set and defaults to false/no:
   
   Default

   - do: something become_user: someone

   1 2 3

   - do: something become_user: someone

…unless become was set to true on a higher level, e.g. a block, the playbook, group or host-vars etc.

Here is an example with a block:

The first 1st is ran as user someone, the 2nd as root.

As I understand it become_user is something similar to su , and become means something like sudo su or “perform all commands as a sudo user”.

The default become_method is sudo, so sudo do something or sudo -u <become_user> do something