I have a certain way of introducing the idea of vowels and consonants. I'm fairly certain it's not research based, but it works for me, and my kids seem to get it.
I start out with this chart, minus everything below the pictures.
We gradually add letters to each side, depending on whether we can feel them or not. In other words, if anything moves or touches in our mouths, we can feel them. (The only one that is tricky is R.) Once all the letters are on the chart, I ask them what they notice. Someone typically figures out that the letters we can't feel are called vowels. That's when I label each side.
This chart certainly doesn't make or break my readers, but when we then start talking about vowels and consonants in more depth, they have something to link those words too.