what are the levels for Delta Skymiles???

[ac921ol]

what are the levels, I saw a diagram of 

25k bronze

50k silver

75k gold

100k platinum

what does that all mean??? wha do I get per level??? all I can see is this MQM stuff which I dont really have. 

[Anf_dude]

I'm Rally Curious Too. I Have 20k SkyMiles Accumulated, But No MQM's.? How Do I Even Earn Those.? This Delta Thing Is Confusing. >_<