A proportion is an equation that uses two equal ratios to find an unknown value, while proportional division splits a whole into parts using a fixed ratio.
An equation stating that two ratios are equal is called a proportion. For example, 2:3 and 4:6 have different numbers but represent the same ratio, so we can write 2:3 = 4:6. The two outer numbers (2 and 6) are called the extremes, and the two inner numbers (3 and 4) are called the means. Whenever a proportion holds, the product of the extremes always equals the product of the means (2×6 = 3×4 = 12). This property lets you find an unknown value quickly with just multiplication, even when one value is missing.
Proportional division works a bit differently. It splits a whole according to a ratio you've already decided on. For example, splitting 20 candies in a 3:2 ratio means treating the whole as 5 equal groups (3+2) and first figuring out how many candies are in one group. Change the ratio and the total with the sliders, and check whether the two resulting shares really do keep the original ratio.