This document discusses long and short vowels in English. It explains that vowels can have long or short sounds depending on their position in a word and surrounding letters. Specifically, it provides examples of when vowels will be long, such as when followed by a single consonant and "e" or when a single vowel appears at the end of a word. It also gives examples of short vowel sounds in words like "map", "egg", and "mug". In total, the document defines vowels, long vowels, and short vowels in English.