A ratio is a way to compare two quantities, showing how much of one thing there is compared to another. The ratio 2:3 means that for every 2 parts of one quantity, there are 3 parts of another. This can be applied in various contexts, such as mixing ingredients in a recipe or comparing the number of boys to girls in a class. For example, if you have 2 apples and want to maintain a 2:3 ratio with 3 oranges, you would need a total of 3 oranges to keep the proportions correct. Ratios help in understanding relationships between different items or groups.