Ships sections come in 4 forms as listed below; in general each section has a concentration cost and min and max applicable category which modifies the effective values of each part. It should also be noted that some categories are restricted from some features due either to limits placed on the ships computer or size restrictions.
Hulls are the primary form of ship sections and generally improve your base stats in a wide range of categories. Hulls usually have relatively low concentration costs in comparison to other section types but also lack any function beyond adjusting base stats.
The second most important grouping of sections is weapons and this is an obvious one, it includes all the parts that get business done including cannons, rays, missiles and even bomb deployment assemblies. Weapons themselves come in 3 types - small, medium and large. This is in addition to the applicable category requirement. Weapons usually have a moderate concentration cost but better weapons do require more skilled pilots to operate.
Of particular interest is the relationship between weapons and fire control modules. Each category of ship has a fixed number of fire control modules i.e. each category of ship can have X number of weapon groups. A weapon group can have as many or as few weapons in it as you like however weapon quarters (see quarters below) require an assigned fire control sub-system and will only apply to the weapons in that group. In addition some weapons have a very high energy use or perhaps have a unique range requirement and so benefit from being fired separately from the usual spray and pray cannons that pilots tend to hold in the firing position.
Quarters are a special grouping of sections that behave much like hulls. They provide small benefits to base stats while also enabling some special features such as salvaging, repairs, anti-electronic warfare and fire direction, in addition to control FDC - a popular form of weapons quarter. FDC staffs a small crew of gunners, spotters and other skilled non-Terran persons to handle one or more fire control modules allowing the Terran pilot to focus on a smaller set of weapon systems with more attention and focus. This is particularly useful on larger ships where the smaller and less powerful weapons will be handed off to an FDC, allowing the pilot to focus on the use of larger more complex weapon arrays to deal with harder targets.
It should be noted that quarters usually require a higher level of concentration as they are staffed by living beings or complex autonomous machines which themselves require a a great deal of support. Quarters will require such things as life support, food, climate control, gravity and so forth to function. While this is a less efficient use per task of concentration, it does allow a larger number of simple tasks to be managed than simple direct control allows for - engaging multiple targets with multiple arrays for example.
Instruments offer no stat benefit but grant specific functions such as salvaging or improved fire control. Instruments are similar to quarters though typically at a lower concentration cost and lower effectiveness. Instrument effects and abilities are typically 'active' meaning they must be turned on and off, while quarter abilities are generally 'passive' - they do what they do automatically though some may take direction such as 'marking' a target.