Vampire already said most of it, but each Hacker foldout serves a specific purpose. I'll give a quick rundown of how Hacking works in AI War.
Hacking Progress, HaP, is used to pay for each hack. You acquire HaP whenever you acquire AI Progress (AIP), but do not lose HaP if the AIP goes down.
HaP costs are fixed for the first hack of each type, then increase by 50% for each additional hack of that type.
The AI's response to your hacking is based on AIP, total HaP spent, and total HaP available. More AIP or less HaP available means a stronger AI response. If you allow the HaP to go negative, the AI's response will increase dramatically. Going very negative is generally not recommended more than once.
- The Covert Knowledge Extractor serves to drain Knowledge from an AI controlled system. This is the same Knowledge pool as you get from your own systems, so has the same 3000 K cap.
- The Research Redirector is used in systems with an Advanced Research Station to allow you to choose which of the three ship designs to unlock when you capture the system. You can see the list of available ship types by bringing a normal Science vessel into the AI's system. If you don't hack, you always get the leftmost one.
- The Fabricator Hacker grants you the ability to produce the Mark V unit that Fabricator produces, without controlling the Fabricator. It can only be performed in an AI system with at least one Fabricator in it. If the system has more than one Fabricator, one hack unlocks all of the units, but counts (for HaP costs and increases) the same as if one hack per Fabricator had been performed.
- The Advanced Construction Hacker allows you to produce Mk IV units of any ship type you have unlocked Mk III for, even if you do not control the Advanced Constructor. The Advanced Factory allows Mk IV fleetships, and the Advanced Starship Constructor allows Mk IV starships. This hacker can only be used in systems with a AF and/or ASC. If both are present, it behaves like the Fabricator hacker, granting both, but costing two hacks worth of HaP.
- The Design Downloader allows you to unlock the Mk I of a new ship type. This hack can only be performed in AI systems where a Design Backup is located, and the ship type unlocked is the one specified on the description of the Backup server. If multiple servers or ship types are present, it acts like the Fabricator (multiple unlocks, multiple costs).
- The Design Corruptor behaves like the Design Downloader, but instead of unlocking a ship type, it prevents the AI from using that ship type. Note that AI Homeworld have their own ship type pool, and cannot be prevented from using units through this hack.
- The Sabotage Hacker destroys the nearest notable AI structure in the current AI system, without imposing an AIP penalty if the structure destruction would normally impose one. When you place a Sabotage Hacker, mousing over the foldout will tell you which structure will be destroyed. This can be performed in any AI system, but will do nothing if there are no notable structure present. The AI Command Station is NOT a notable structure that can be sabotaged.
- The Sensor Hacker gives a brief period that uncloaks all AI units, and applies cloaking to all Human and Allied units in that AI system. This can be performed in any AI system.
- The Nomad Beacon Hacker is part of the Nomad Planets questline. It can only be performed on an AI controlled Nomad 1 system, where the Nomad Beacon is present.
- The Exile Survey Hacker is part of the Exile questline, and can be performed in any AI system.
Finally, the last hack doesn't use a Hacker foldout. The AI SuperTerminal can be 'hacker' by building a Human Command Station in the system that contains the AI SuperTerminal structure, after destroying the AI Command Station. This hack uses HaP continuously as long as the SuperTerminal remains, and can only be stopped by destroying the SuperTerminal structure.