Vowels are speech sounds that are made by our vocal bands. They also happen to be five / twenty-sixth of our alphabet. Depending on how a vowel sound is stressed within a word determines the classification of a vowel. There are two standard classifications. Long vowels are vowels that sound the same as the letter that they represent. For example, in the word “bake”, the vowel a is said the same exact way as you say it when reciting the alphabet for your teacher. Short vowels do not have the same sound within a word as they do within the alphabet. For example, the vowel a in the word “apple”. If you look at the entire language short vowels are much more common. The best way to identify the use of a long and short a vowel is to say the word aloud to yourself and ask yourself if the vowel sound is the same as the name of the vowel. If the vowel (in this case "a") says it's name, it is consider a long vowel. Such as in the word "take". If the vowel does not do that and make another sound, it's considered a short vowel.
Many people don't understand the importance of understanding long and short vowels. It becomes a very valuable skill once you start to encountering higher level vocabulary words. The most common long a words are: baby, lady, paper, bake, rake and lane. The most common short a words are: dad, hat, man, sat, fan and lane.