What type of steel and why?

[blitztech]

I'm trying to gain some insight in to the different types of steel used in production knives. High to low quality, what makes it high quality, and hardness. Which types retain an edge longer. Why would you choose a steel that doesn't retain an edge as well? Teach me what you know. I've read some sites online, but they all get very technical and I'm looking for info that's simplified. I'm not trying to make my own, just want to become an informed consumer.