When linguists describe vowels, they use a chart to classify them into either high, mid, or low, and into front or back. I have included a picture of this chart for your reference.
Whether a vowel is high, mid, or low depends on where it is produced in the mouth--for example, a long "E" sound (represented on the chart by the International Phonetic Alphabet symbol "i") is a high vowel, because the tongue is almost touching the roof of the mouth and the jaw is held in a high position. By contrast, the "AH" sound is low, because the mouth needs to hang open in order to say it, meaning that the jaw is held low.
The other criteria is whether a vowel is front or back. Again, the "E" sound is obviously very forward in the mouth (you can tell by the forward position of the tongue), making it a front vowel.
A final criterion linguists use is whether or not a vowel is rounded; this is easy enough to figure out, as a rounded vowel requires the lips to come together (as when we say the "OH" sound).
Linguists will string all these adjectives together when describing a vowel. So, the "E" sound we've been talking about would be called the "high front unrounded" vowel.
The 5 English vowels are a, e, i, o, and u.
Each can have a long sound and a short sound. The long sound primarily sounds as an identification of the vowel. Long vowel sounds are often in play when two vowels are working together. For example, the words paid, play, and made all contain the long A sound, and they are working with another vowel somewhere in the word.
Short sounds are often used when they work alone and on their own. For example, the words dot, on, and shod.
Sometimes, vowels work with consonants or other vowels to make a different sound that doesn't follow the above rules, but makes another sound. Some of those combinations in words are aw, au, oo, ow, and ou.
I recommend searching the term phonics, and then within that, search vowel rules.
When we speak, all the sounds produced by us are classified in two type of sounds. These are vowels and consonants. The sound of vowels is made with free passage of breath. In English, the vowel sounds are represented by the letters, a, e, i, o, u, and sometimes w and y (as in now, city). But each letter stands for several sounds.
Consonants are formed with the organs of speech more or less closed. A vowel may be a syllable in itself, or it may be joined with one or more consonants to produce a syllable.