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.
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.
Real-world example: 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.