OIC - Difference between Oracle Databse adapter, DBaaS adapter and ATP adapter

Database Adapter:

It is used to connect the On-premise Databse which is installed behind the firewall, it needs an agent to connect to/from OIC.

DBaaS Adapter:

It is used to connect Database Cloud Services hosted on PaaS platform on Oracld Cloud Infrastructure. This also needs an agent to connect to/from OIC.

ATP Adapter:

It is used to connect Autonomous Transaction Processing(ATP) database which is a PaaS offering by Oracle. It does not require any agent rather it require wallet to connect to /from OIC