Singing vowels not correlating with alphabet vowels?

Hey I Don’t really understand that when you talk about vowels in singing you say "ee oo hey yeah uh" but the vowels in the alphabet are aeiou? Which corresponds to which?

I understand: ee = e, oo = o but what are the rest?

Sorry if this is a dumb question!

A=Ah, E=Eh, I=EE, O=OH, U=OO (in the "Latin vowels" exercise). Not a dumb question at all! They are the Latin pronunciation of those vowels (also similar to the same Spanish vowels). 

Haha that's so confusing! I guess I'll have to get used to it! Which vowels are in hey yeah uh? (Sorry if you already answered it I'm still a bit confused)

Those 5 Latin vowel sounds don't include every vowel sound in the English language! Here's a more complete list: https://simple.wikipedia.org/wiki/Vowel.