Spinor Particles :

The property of Spin of a thing
describes
how that thing is transformed
if you rotate it in space by 360 degrees.
For instance, take an arrow from a bow and arrow set, and consider that the arrow points in the direction from its tail to its arrowhead.

If you rotate the arrow tail to head, by 180 degrees, the direction of the arrow is reversed, so a 180 degree rotation reverses the arrow.

If you continue the rotation by another 180 degrees, you have rotated the arrow by 360 degrees, and the arrow is back where it started.

Since the arrow is back to where it started after 1 full 360 degree rotation, the arrow is said to have Spin = 1.

Unlike the arrow, the Particle Actors described by E6
are NOT back where they started after 1 full 360 degree rotation.

It takes two full rotations, 720 degrees,
to get an E6 Particle Actor back where it started.

Since an E6 Particle Actor is only 1/2 back to where it started
after 1 full 360 degree rotation,
an E6 Particle Actor is said to have Spin = 1/2,
and
is called Spinor since its Spin is not the simplest value 1.

Lest you think that the requirement of 720 degree rotation
to get something back to where it started
is something
that does not happen in our "normal" world,
and
is something that only happens in a "weird-physics" world,

you should know
that there ARE ways to demonstrate Spinors,
based on
the "orientation" of the thing being rotated
with respect to its "environment".

Here is a demonstration of Spinor Orientation-Entanglement:
Louis H. Kauffman, in his book Knots and Physics (World Scientific Publishing Co. 1991), says that a spin 1/2 particle is like a ball attached to its surroundings by string, as in this picture from Gravitation, by Misner, Thorne, and Wheeler (Freeman 1972):


The orientation of the ball is related to the surrounding sphere by the tangle of the strings connecting them. If you rotate the ball 360 degrees, the strings are tangled, but if you go to 720 degrees, the strings get untangled. Here is a demonstration of how the 720 degree (4 pi) rotation works:


It is from Feynman's 1986 Dirac Memorial Lecture (Elementary Particles and the Laws of Physics, Cambridge Press 1987), and it shows a cup held by a dancer in one hand. Rotating the cup by 360 degrees gets the arm (which is connected to the shoulder of the dancer) twisted, but turning the cup another 360 degrees gets the arm back straight.

In it, picture 1 is the start, picture 2 is 180 degrees, picture 3 is 360 degrees (note how the arm is twisted), picture 4 is 540 degrees, and picture 1 again is 720 degrees.

The spin 1/2 particles orientation-entangled with their environment are Fermions and their intrinsic orientation-entanglement can be mathematically described by saying that Fermions are Quaternionic.