To subtract fractions, you need to have a common denominator. In this case, the common denominator is 6.
2/3 can be written as 4/6 (by multiplying the numerator and denominator by 2).
1/2 can be written as 3/6 (by multiplying the numerator and denominator by 3).
Now you can subtract them:
4/6 - 3/6 = 1/6
So, 2/3 - 1/2 is equal to 1/6.