What is a quaternion? And how is it used in graphics?

Question

I've seen other stackoverflow answers such as

What's a quaternion rotation?

but I'm still not sure what they are

When I looked it up on Wikipedia, it gave me a 4-dimensional imaginary coordinate space.

Can anyone explain to me what they are in the most intuitive sense please? And how they are used in computer graphics?

Answer 1

A Quaternion is a 3D vector with a rotation. For using them in OpenGL, I found a link for you: OpenGL Rotations