An "ideal type" is a way of describing something that doesn't really exist in exactly the same way in real life, but it's a good way to help us understand and talk about things. It's like when you talk about a fairy tale princess - she isn't a real person, but we can use her as an example to help explain things.
When people talk about an "ideal type" they mean a kind of perfect example of a thing or person. But it isn't something that we can actually find in real life - it's more like a made-up picture in our heads that helps us understand what we're talking about.
For example, if we're talking about a perfect student, we might describe them as someone who always does their homework, listens to their teachers, and gets really good grades. But even if there are students who do those things, no one is perfect all the time. So the "ideal type" is more of an imaginary picture we can use to help us talk about what we want students to be like.