Combat in EVE is the fine art of doing as much damage as possible to your enemy's ships. To do this, you have to understand how your weapons work and how to make the best use of them. This page explains the essential technical details of combat that every capsuleer should know.
Weapons in EVE Online have various characteristics that affect how they shoot. Among the most important of these are accuracy falloff and optimal range. These details tell you the best distance at which to keep your enemies to have the highest probability of doing the most damage.
Optimal range is the ideal distance from which to shoot your weapon. If you can keep an enemy at exactly the optimal range of a weapon, then that weapon will theoretically never miss that enemy. However, other factors come into play, such as tracking speed, that will reduce the effective accuracy of the weapon.
Accuracy falloff tells you how far away your weapon can be from optimal range and still have at least a 50% chance of hitting the enemy. So, if your weapon's optimal range is 10000 m and your accuracy falloff is 3000 m, then if you are 13000 m away from the enemy, your weapon will have about 50% chance of hitting the enemy.
If your distance from the enemy is two times the accuracy falloff, plus the optimal range, your weapon will always miss the target. If your weapon's optimal range is 10000 m and your accuracy falloff is 3000 m, then if you are 16000m or farther away from the enemy, your weapon will not be able to hit the enemy at all.
During combat, you can right-click on a moving object and choose "Keep in Range" to make your ship attempt to stay at a specific distance away. However, if the target is faster than your ship, you might not be able to stay at your desired range.
Some types of weapons have a tracking speed. This is a measure of how quickly the weapon is able to rotate.
Angular velocity is a measure of how quickly an object is rotating relative to your ship.
If an object is orbiting your ship more quickly than your weapon's tracking speed, that weapon will have a reduced probability of hitting the enemy. On the other hand, if you are orbiting your enemy quickly, the enemy will have a lower chance of hitting you.
Keep your tracking speed in mind, especially in situations of close combat with fast ships.
You can target a moving object and choose to orbit it at a specific distance. Orbiting an enemy can make it more difficult for that enemy to hit you, but your own accuracy will also be reduced.
The signature resolution of a turret is a measure of how big a target has to be for that turret to hit it accurately. The signature radius of an object is a measure of how big or small the turret thinks that object is. If a turret has a small number for its signature resolution, it will be able to target small objects with good accuracy.
Ammunition can inflict four types of damage: electromagnetic, thermal, kinetic, and explosive. A ship's shield and hull may be stronger or weaker against specific types of damage. If you are able to research your enemies before engaging in combat with them, you may be able to find out which types of damage their ships are less or more resistant against so you can choose your ammo accordingly.
You can fit modules to your ship that interfere with your enemies' electronic systems, and your enemies may also make use of such modules. This is known as electronic warfare, or EWAR. In EWAR, you can make it harder for your enemies to target you or hit you. You can also restrict your enemies' ability to move and warp. Your enemies can do this to you as well.
The tactical overlay is a view that you can turn on while you're in your ship by pressing the button with the target on it to the left of the capacitor. It shows concentric rings centered on your ship.
The concentric rings denote the distance, in km, from your ship.
When you hover over a weapon turret or other type of module restricted by distance, a sphere or two will appear around your ship.
If you see two spheres around your ship, this means that the turret that you are hovering the mouse cursor over has an optimal range and a falloff range.
The inner sphere always shows your optimal range. Enemy ships on or near that sphere are in your optimal range, where your turrets have the best chance to hit them. It doesn't affect how much damage you deal; it just denotes how likely your weapons are to hit the enemies.
However, as mentioned above, your turret tracking speed will also affect how likely you are to hit the enemies, to the point that even if a ship is in your optimal range, you could still miss if the ship is circling you faster than your turrets' tracking range. In other words, optimal range is not a guarantee of hitting the target.
The outer sphere represents your optimal range plus falloff range. If you try to hit an enemy that is outside of the outer sphere, you are unlikely to successfully hit the enemy.