What is the explanation of automatic transmition on 1989 Buick Century Limited?

I have purchased an 1989 Buick Century Limited. I love the car, but unfortunately can't find any information about this nice car: operation, maintanance, consumabiles, etcWhat is the explanation of automatic transmition on 1989 Buick Century Limited?An automatic transmission shifts itself, you simply choose forward or reverse with a hand lever. A manual transmission uses a foot clutch and requires changing each gear manualy as necessary.