Electromagnetic damage is one of the four main damage types encountered in space combat, and usually shown with Blue icons and missile tips.
In general, Shields have negligible resistance to EM weaponary (typically 0% resist), but ship Armor provides very strong resistance against it (typically ~60% resist). These resistances may be increased with the appropriate active or passive Hardener modules.
All Laser weapons do some degree of EM damage, although the proportion depends on the selected charge crystal. Some types of Projectile ammunition also do EM damage. No Hybrid weapon is capable of EM damage.
Blood Raiders NPC Pirates commonly use laser weapons, and so can be expected to deal EM damage.
Tactically, due to the general lack of shield EM resistance, EM weaponary is best used to open an engagement only. Once the enemy's shields are down, it is best to switch to a type that is less resisted by armor, such as Explosive. A pairing of EM and Explosive damage types can yield the most effective damage-over-time during a single fight, but requires the most precise timing on the switchover when the target's shields have failed, to be effective. With multiple targets, in various states of shield strength, a more general purpose damage type may be more effective, such as Thermal or Kinetic.