What’s the difference between “Going out”, “Going steady” and “Being someone’s girlfriend” ?

I've seen these phrases a lot on American TV from the 90's but don't exactly know what the difference is.

I thought going out meant casual dating and going steady meant you were committed. But then they would say something along the lines of "Do you want to be my girlfriend/ I wanna make it official" and I guess that's a whole other thing. And all of this comes before anyone says "I love you". Lol.