Im confused about the three groups of consonants:
semivowels
mutes
double consonants
Can someone direct me to where these are explaned or explan them
We have a tutorial on the consonants, Phonetics 101: The Consonants where some of this terminology is explained.
Double consonants are just like when any two consonant sounds run into each other, such as “sick knight”, except that the two are the same, “sick king.” If you pronounce these two examples, you’ll notice a characteristic delay over the second example. In some languages these double consonants can occur in the middle of any word, not just when different words run into each other. In Greek, ἄλον is a different word than ἄλλον, and they were pronounced differently.