We live in a 3D universe
Draw the X, Y, and Z axes.
There are six points on these 3 lines
Now, if you make each line the same length
And draw lines connecting the end points
That looks like a 3D cube with transparent faces
So that you can see all 12 edges of the cube
Now, draw a green diagonal line across the 3 faces that are visible
And a red diagonal line across the 3 that are not visible.
GEOMETRY is a branch of mathematics