How are proportions and fractions different?

Answer 1

Yes. Fractions refer to the same thing whereas proportions may refer to different objects.

For example, 1 egg is 1/200 of 200 eggs,

100 grams of flour make 1/400 of 40000 grams of flour. Both these are fractions.

However, 1 egg to 200 grams of flour is a proportion. One egg is not 1/200 of 200 grams of flour!

Answer 2

Fractions are comparisons of amounts of the same thing or in the same units, proportions need not be.

For example, a recipe may require 2 eggs for 250 grams of flour. An equivalent proportion is 1 egg per 125 grams of flour. However, there is no fractional relationship. One egg is not 1/125 of a gram of flour