Same amount, different name.
1/2 is the same as 2/4, 3/6, and 50/100.
Crucial for adding fractions with different denominators.
Whatever you multiply the top by, multiply the bottom by.
In Plain English: If you cut a cake into 2 pieces and eat 1, it's the same amount of cake as cutting it into 100 pieces and eating 50. The numbers change, but the hunger satisfied is the same.
In The Real World: Cooking. If a recipe calls for 1/2 cup of sugar but you only have a 1/4 cup scoop, you use 2 scoops (2/4).
Adding to the top and bottom instead of multiplying. 1/2 is NOT the same as (1+1)/(2+1) = 2/3.