Reguarding the Q1, Q2, Q3... 3LEMENT0 said it right, but just to get rid of any confusion you might have left, it refers to the quarters of the year (12 months in a year, divide by 4 since it's being done by quarters) You end up 3 months equals 1 quarter. So, like he said:
Quarter 1 of the year is January, February, and March
Quarter 2 of the year is April, May, and June
so on and so forth...
if there were a quarter 5 you would need more than 12 months in a year or that would go into the next year, because you can't really have 5 fourths in a year.
Hope that clears things up....