Electronic Warfare (or EWAR) is one of the most underrated parts of PVP in Eve Online. It's classed as a force multiplier, meaning that it supports and enhances any fleet it is part of, whilst negatively affecting any hostile fleets through a number of means.

If you are past the basics, try Advanced Electronic Warfare

There are four major types of EWAR and each type has it's own counter measure.

ECM focuses on breaking and preventing ships from targeting and locking other ships

Sensor Dampening focuses on reducing ships targeting range and lock time

Target Painting focuses on increasing ships signature radius increasing the chance of being hit by weapons and drones

Tracking Disruption focuses on reducing the tracking speed and chance of being hit by projectile-based weapons.

The following ships are stocked in Test Free:

• Maulus (Sensor Dampening)
• Maulus (Target Jamming)
• Vigil (Target Painting)
• Celestis (Sensor Dampening)
• Blackbird (Target Jamming)

• http://wiki.eveuniversity.org/EWAR_Guide
• https://www.themittani.com/features/ewar-newbies
• http://jestertrek.blogspot.co.uk/2011/03/class-pvp-103-electronic-warfare.html