Now, a good consonant definition, in term of pronunciation, is that with consonants, the articulators either touch or they come are very, very close to one another.
So, in answer to your question, 'what is a vowel', well, a good definition is that vowels are made with the articulators holding a shape but not actually touching.
What's weird is that all these different sounds made with different articulators are represented with just one symbol and considered to be part of the same phonetic family, known as rhotics.
Well, a good definition of consonance sounds is that it is a sound whereby the articulators either touch or almost touch and then releasing suddenly or slowly or they hold their position.
The different moving parts are known as articulators, and the main ones are the tongue, upper lip, lower lip, upper teeth, alveolar ridge, hard palate, soft palate, uvula, the pharyngeal wall, and the glottis.
And with the OO vowel sound, as in 'who', 'shoe' and 'move', the lips are rounded and the back of the tongue is high but again, nothing actually touches, it just, the articulators just hold a shape.
Now, we do have 3 consonants that don't follow that rule exactly, in fact, they don't touch, the articulators don't touch with these three consonants, instead the articulators approximate with one another.