There are five vowels in the Spanish language. They are a, e, i, o, and u. What is nice about the Spanish language is that each vowel has only one sound. In English, the same five vowels have 12 different sounds. This makes it easier to learn and pronounce Spanish words. The vowel a is pronounced "ah". The vowel e is pronounced "eh". The vowel i is pronounced "ee". The vowel o is pronounced "oh". Finally, the vowel u is pronounced "oo". There is something called diphthongs in the Spanish language which also is involved in pronouncing vowel combinations, but that answer is for another question on another day. Knowing how to pronounce the vowels helps in learning and correctly pronouncing words in Spanish.
Like in English, the Spanish vowels are a, e, i, o, u, & sometimes y. However, unlike English, each vowel can be pronounced only one way:
a like in father
e like in ate
i like in eat
o like in ghost
u like in boot
y like in eat when it's by itself or at the end of a word
In English, we THINK there are only 5 vowels, but there are just 5 symbols. There are actually over twice that many SOUNDS. Consider:
father fat fate
The most common vowel sound in English is a sort of "uh" sound. Spanish doesn't have that sound, so be sure all your vowels sound like one of the five choices above.