What is Blitz chess?

A game with a time control of less than 15 minutes and greater than or equal to 3 minutes is  'blitz' chess. Blitz is one of the rating categories in your personal profile or 'finger'

The exact boundary between 'blitz' and 'bullet' or 'standard' is defined by 'etime'.
Etime is the time + 2/3 increment.
Bullet       -- Games with etime < 3
Blitz         -- Games with 3 <= etime < 15
Standard -- Games with etime >= 15
A bullet game is 0 1,  0 2,  0 3,  0 4,  1 0,  1 1,  1 2,  2 0  or  2 1.
A blitz game is 0 5 - 22,  1 3 - 20,  2 2 - 19,  3 0 - 17,  4 0 - 16,  5 0 - 14, 
6 0 - 13,  7 0 - 11,  8 0 - 10,  9 0 - 8,  10 0 - 7,  11 0 - 5,  12 0 - 4,  13 0 - 2,  14 0 - 1.
(0 5 - 22 stands for 0 5,  0 6,  0 7,  0 8,  ---   0 21,  0 22)
Standard is the rest with the maximum time control of 600 300

Blitz time control games count towards your blitz rating, not your bullet or standard rating. Games played in the 3-minute and 5-minute pool count towards the 3-minute or 5-minute rating, not the blitz rating.
For more information read  "help etime"