What do the letters and numbers mean for the ar codes?

They're hexadecimal numbers. Hexadecimal numbers, unlike the decimal numbers that we usually use, have a base of 16 while decimal numbers have a base of 10 (hence the word hexadecimal, which comes from the Greek hexa, meaning 'six', and Latin decium, meaning 'ten'). Hexadecimal numbers incorporate the first Arabic numerical figures (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9) as well as the letters A (10), B (11), C (12), D (13), E (14), and F (15). Because of this, 16 is written 10, and 255 is written FF.

The place values for hexadecimal numbers are weighted on 16, so reading them can be done thus: We have a hex number A7, which translates to 167 given: A7 = (16¹ � A) + (16⁰ � 7) = 160 + 7 = 167, since A = 10. The pattern for place values can be interpreted by using the variable n in the pattern 16^{n � 1} � V, with n � 1, which is the number of places to the left of the decimal point minus one, being the power of 16 and V being the decimal equivalent of the hex digit. Thus, 4 in the third place from the left (41C) in hexadecimal is really 4 � 16² + 1 � 16 + 12 � 1 = 4 � 256 + 1 � 16 + 12 � 1 = 1052. So the first four places are 1, 16, 256, and 4096.

Cross Stinger has explained it all to you, but I will put it simply: They are the numbers and letters that make up the data necessary to be matched up with the game's data to be activated so that your game can be enhanced...

They are computer code which programs all video games. The code is added to change the game.