system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] How does deflecting blaster fire with a lightsaber work? What keeps the blaster fire from splintering into a rain of smaller blaster bolts when it hits a lightsaber or getting absorb by the lightsaber entirely like the shots from a training remote?
gpt
Blaster bolts are either plasma or high energy particles held in place by a magnetic bubble.  When they strike a target, that bubble dissipates, releasing its contents to "splash" the target with the plasma/particles.  Similarly a lightsaber is plasma held in place by a magnetic field.  When it strikes a target, that magnetic field is selectively disrupted at the point of impact and heat of the plasma is released.

When a blaster bolt strikes a lightsaber, the magnetic bubble of the blaster bolt and the magnetic field of the lightsaber have a fully elastic collision, so neither the bolt nor the lightsaber are disrupted.  Both bounce back from the collision.  However since the momentum involved is fairly low (momentum = velocity \* mass and the mass involved is incredibly low), the bounce back of the lightsaber is easily compensated for by the muscles of the wielder, while the bolt is reflected back at the shooter or another target guided by a combination of physics and the force.

Ray shielding works against blasters in a very similar fashion.  The magnetic bubble of the blaster bounces off the magnetic field of the shield.