The document discusses ratios and proportions. It defines a ratio as comparing parts to parts, such as two to every three, while a proportion compares a part to the whole, such as two out of five. Examples are provided of calculating ratios and proportions, including determining the ratio of red to white objects and the proportion of a shape that is red or white. The document also provides a word problem using ratios to determine the total number of songs played based on the ratio of new to old songs.