Thruster Module
This article details the existence and use of a Thruster Module
The Essentials
A Thruster Module (Formerly known as a Hypercoil Thruster) is required to give a ship propulsion, and subsequently, the ability to move. While a core on it's own contains a small amount of thrust, if a player wants anything to move at a decent speed then Thruster Modules will be required.
Every Thruster Module placed adds a fixed amount of thrust per block (1.7 thrust per block with thrust diverted equally)
Module Use
Thrusters are very commonly used for decorative purposes, either in large groups or scattered around individually. Thruster Module do not gain any additional bonuses from being adjacent to another Thruster Module, and so may be placed freely without any constraints. Often times it's seen as a good idea to have small groups of thrusters separated around a ship, so that it's harder to target them down and shut down a ship's movement. While it may be difficult with the many other modules in place, it's certainly recommended for absolute safety.
Not only that, but considering the amount of thruster modules often needed, while uncommon, they can be used as a "system shield" to layer over other more important/more expensive systems so as to keep them safer, possibly increasing a ship's combat endurance. This ultimately depends on the ship and it's role, but for say a brawler where speed is not exactly important, it could be a good idea to use Thruster Modules to protect the more defensive/tanky modules.
Thrust carries between entities. You may have a separate entity made up entirely of Thruster Modules, and dock it to a much larger ship, giving the parent ship the thrust from the child ship. However, this is EXTREMELY inefficient, as thrust transferred from a child to parent is reduced to 1/8th of the original thrust per entity it's travelling through.