GitHub apps can be owned by personal accounts or by organizations

They can be GitHub apps or OAuth apps

GitHub Apps owned by personal accounts are accessed in https://github.com/settings/apps
and OAuth Apps https://github.com/settings/developers

Apps owned by an org are accessed in https://github.com/organizations/andres-test-org/settings/apps (Organization Settings -> Developer Settings).
This is different from an Organization's installed apps (Organization Settings -> )

Difference between GitHub Apps and OAuth App

The main difference is that GitHub Apps are designed for fine-grained permissions and can act as a bot, while OAuth Apps use broad scopes and always act on behalf of a user.

In general, GitHub Apps are the newer, preferred way to build integrations.