Help with difference in class of fares
I am trying to book really cheap tickets MSP -MCO for June, I have an option of $109, $129, $180 etc.
What is the difference between Q class at $109 and K class at $129?
And M class and B class at $180 and $ 215?
And is there any real problem with getting a seat at check-in, other than having to sit in a middle seat?