erm... 1 and 2 are both positive integers, written in Arabic numerals. Both are also part of the base numbers in any numerical system above binairy. 1 is odd, whereas 2 is even. 2 is also a prime number while 1 isn't. Can't quite think of any other similarities/differences of any significance between the two.
Now to explain them.
Let's see. Both are written in Arabic numerals due to strong Arabic influences in the Dark Ages I presume. 1 is odd, because dividing by 2 doesn't return an integer, which 2 does. 2 is a prime number because it only returns an integer when divided by one, or itself. 1 isn't a prime number due to dividing by 1 being exaclty the same as dividing by itself.
Is this the intended awnser?
EDIT: 1 requires less ink when writing than 2, and would use less memory on a computer using a binairy system, if numbers weren't saved in bit words of predetermined length.