A fraction is a portion of a whole number the same as a decimal. Think of money - 75 cents is a fraction of $1.00 and a dollar is 100 pennies so you can write it as a fraction 75/100 or reduce it to 3/4. You know it takes 4 quarters to make a dollar, so if you only have 3, you only have a fraction of the whole dollar. By using quarters we broke the whole number up into fractional shares of the whole. 4 quarters (1/4 +1/4 + 1/4 +1/4 = 4/4 or one whole)
Fractions are simply division problems. For example 3/4 becomes the division problem 3 divided by 4 which will result in the decimal .75 (we're back to our original 75 cents). The 3 is the dividend, the 4 is the divisor and the answer is the quotient.
In addition, think of bottom number (the denominator) of a fraction as a whole pizza that you have cut up into a number of pieces - in this case 66 pieces. The top number (the numerator) can be thought of as how many pieces out the entire pizza did you eat - in this case 66, so you ate 1 whole pizza.
In the case of 66/66 you would be dividing 66 by 66 and any number divided by itself equals 1. In this case you had two equal fractions that were both negative , so you were dividing a number by itself, therefore it is positive one.
Whenever you divide or multiple 2 negative numbers, you end up with a positive.