Space, according to the grand unified theory of the cosmos, is basically flat and empty, with gravity acting like balll bearings on a rubber sheet about collections of matter. In EVE, where gravity is a nonevent, space is essentially flat and empty. It really should have no benefits to the attacker or defender.
However, this is not the case. Terrain in EVE is a concept I have to take into consideration when FCing. EVE Terrain within a system consists of four elements; distance, cover, obstacles and effects.
Distance is fairly obvious. If you have an opportunity to attack a foe and you aren't soloing, you have to weigh your tank versus his gank versus the time it willl take for backup to arrive. Likewise, distance impacts upon Cover, as distance is itself a form of cover or concealment - being more than 14 AU away from a foe renders you practically invisible.
Cover is not simply governed by the limits of the directional scanner, although this is obviously a huge factor, especially if you are launching combat probes to scan down an enemy. If you are beyond d-scan range, say at a deep safe, you can assemble a gang which is far superior to the enemy, without his knowledge of exactly what you have. Similarly, stations work like cover, concealing the ship you play in the fight until it undocks - and if a fight is going on, often people aren't d-scanning, which allows you to undock a trump card. To a lesser extent, a POS with an SMA works like that, too. And obviously, cloaking is the ultimate in cover, even in k-space, but obviously in w-space.
Obstacles, particularly warp disruption bubbles, are a key element in nullsec and w-space battles, although in the latter it is often as dangerous to the defender as it is to the aggressor, who will be just as caught by warping into a bubbled wormhole as the guy who has just jumped through.
Effects, particularly wormhole system effects, and incursion effects, are considerations which you also have to take into account. Likewise, the local rats in lowsec or nullsec are important if you are trying to, for example, gank carriers which are ratting anomalies, as you have to tank for their damage, and deal off-spec damage to an enemy who is most likely tanked against the rats.
The interplay between these elements give particular systems a different terrain feel.
For example a 120 AU diameter system is much harder to PVP in than a 8 Au diameter system, because you can have up to 3 minutes to wait for backup, and the enemy will have 3 minutes to react to a new presence in local. This favours the defenders in k-space, but in w-space, with so much absolute cover around for uncloaked ships, it favours the attacker - who can only reliably be detected in the inevitable safe spot he will spawn the moment he hits system, with deep space probes (if you have them).
Likewise, various constellations in k-space haave different terrain feel. Some constellations in perrigen Falls are all +60 Au systems, making it slow to move around. Some ring-road routes through some regions are faster with some jumps than others, due to shorter warps.
Two nights ago we ended up in Oasa in the D4J-PP and 4ZX-C8 constellations, which are in the Jokers sov space. These guys are massively bearing it up, and every gate in the dog-leg constellation had a minimum of 6 tech 1 large bubbles. This presented extreme difficulties in roaming around, as you had huge obstacles to traverse in order to get into warp. However, it would be great BLOPs territory, as the locals are fairly naive and ignorant about neutrals in Local. Our roam sputtered out, as we realised that the terrain was against us, with too much boggy ground, and our BLOPs capabilities were minimal.
Thus, as previously mentioned, a good general should study his maps. Part of that study is to understand the terrain; the interplay of constellation-wide terrain, the in-system terrain, and so on.
The best part of EVE terrain? Wormholes, which break the terrain. A wormhole in system allows you to hide in a fold in space, utterly invisible behind a crease in reality, and leap from nowhere to deliver sudden buggery. A wormhole allows you access to regions and constellations and security divisions of k-space you would have to spend 60 jumps to go visit. Wormholes allow you to bypass the gate camps and death spots (Rancer, Amamake) and the interface systems between low-null and high-low.
Wormholes are like tunnels under the walls of the great fortresses of nullsec, or the great border fences of the mighty empires, allowing you to smuggle in arms and drugs and ships, or just go muck the place up a bit.
Understanding them is key.