Imagine you are playing with a toy that can move in all directions like a ball. Now imagine a space where you can move the toy ball in any direction, not just up, down, left, and right, but also in a twisted, curved way. This kind of space is called a manifold.
Now, let's talk about quaternions. Quaternions are like complex numbers but with more dimensions. Instead of just one imaginary unit, there are three. Just like with complex numbers, quaternions can also be used to represent rotations in three-dimensional space.
So, a quaternionic manifold is a space where instead of regular numbers or complex numbers or vectors, you use quaternions to describe the position and movement of objects in that space. It's a way to mathematically describe a space that allows for twisty, curved movement using quaternions.
This concept is important because it has applications in fields like physics and robotics where movement in three-dimensional space needs to be described mathematically using a more advanced system than just regular numbers.