There are two main types of shields
in the Star Wars Universe - Particle and Energy. Particle shields protect
against physical object including micrometeorites, dust and missiles.
They are used at all times and if a starship lowers its particle shields
reduce the HULL code by -2D. Energy shields (also known as combat shields)
are designed to deflect/absorb energy weapons. So in effect an X-wing
is made up of 2D of hull, 2D of particle shielding and 1D of energy shields.
The 'Shields' characteristic on a starship represents the starship's combat
shields and hence energy shields. So, from above it's clear that a starship's
'Shields' Characteristic DOES NOT affect projectile weapons.
Particle shields DO however protect a starship from blaster based weaponry.
This is because blaster bolts are similar to plasma, which is made up
of both energy and physical components. As a result both energy and particle
shields affect blaster based weaponry. In addition, you can also view
particle shields as hull integrity fields as well.
Other names used instead of 'Energy Shields': Deflector
shields, Ray shields & Combat shields.
Other names used instead of 'Particle Shields':
Hull integrity fields.