Lift axles and double steering axles… purpose?

Tach, I think that some truck drivers are getting busy here and hope that they will give me an answer here to the following question (which I have actually been busy for 25 years since I saw one with a “brause truck”): what sense and purpose actually have lift axles or double steering axles (don’t hit me, I don’t know how the things are called normally, am not a truck driver). I have often seen on the highway that the 2nd steering axle (the double steering axle) is also the second steering axle (the double steering axle). I hope you understand what I mean. Greetings Guensal example: