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 two different types of Electronic Warfare, major and minor. Major Electronic Warfare are specifically designed to disable a ships offensive capabilities. Minor Electronic Warfare is designed to prevent ships from escaping combat scenarios.
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.
Warp Disruption is the use of Warp Disruptors and Warp Scramblers to prevent ships from warping off. This does not prevent ships from using gates.
Bubbles are large spheres which prevent warping in an area. They come in two flavors: anchored and deployed. Anchored bubbles are permanent until they are destroyed. Deployed bubbles last 2 minutes if used by an Interdictor and until the module is turned off if used by a Heavy Interdictor. This does not prevent ships from using gates.
Webs slow a ships velocity by a significant amount which can allow ships to close the distance to them much more quickly.