Start from zero — the basic math you need before everything else
A ratio compares two amounts by division. When you write 3:2, you're saying "for every 3 of this, there are 2 of that." A rate is a ratio where the two amounts are measured in different units, like kilometres per hour. A proportion is just a statement that two ratios describe the same comparison, even when the numbers on the page look different.
Picture a bottle of cordial with a mixing rule on the label: 1 part cordial to 4 parts water. You could follow that rule with a tiny measuring cap for one glass, or with a huge jug for a picnic. The cap and the jug hold very different amounts of liquid, but as long as you multiply both the cordial and the water by the same amount, every glass tastes exactly the same. That's really what a ratio is about: not the size of the amounts, but how they compare to each other.
Try building your own batch below. Set how many parts of cordial and water you want, then drag the batch slider up and watch the cups grow while the ratio between them stays exactly the same.