You can just Google it. It's not a complex answer:

- Snapdragon 8 is the highest-end mobile SOC line, as opposed to midrange Snapdragon 7 and low-end Snapdragon 4.

- Elite means that the CPU core is Snapdragon Oryon, and not Arm Cortex off-the-shelf designs.

- Extreme is a trim/upgrade package that gives the GPU more power and performance headroom.

- Gen 6 tells you the generation of chip from that line.

You should refer to prior discussions on this topic if you're genuinely confused, or somehow think that Apple has a superior taxonomy: https://news.ycombinator.com/item?id=50116504