MODULES: Frame Shift Drive - #00047
Frame Shift Drives are one of the less complex things in Elite Dangerous.
They are solely responsible for your jump range in between systems. They have zero effect on your SuperCruise performance and on movements in normal speed mode.
The regular module descriptions in terms of numbers (1..8) for size and qualities (A..E) apply, as with all core modules.
Except when building a vessel for in-system combat action that doesn't jump to other systems except for 'opting out' from a lost fight, you should always use the highest number available. Jump range is degraded horribly by using a Frame Shift Drive of sub-maximum size.
You should avoid using FSD modules of 'E' quality for their low integrity and bad performance. 'E' rated Frame Shift Drives are rarely good for anything. That's why you should never buy a ship without enough extra money for a decent outfitting. You save for that 'bigger freighter' for days or weeks, then you have to realise that thing doesn't have the jump range for that lucrative trade route. Painful.
You should only consider using FSD modules of 'D' quality for combat ships or similar. These modules are light, but their integrity is the lowest of all versions. Be aware that once being shields down you got a high chance of being hindered from jumping to a safe system with only a small amount of damage to your Frame Shift Drive module.
'C' rated Frame Shift Drives can have enough range for some purposes. They're far worse in performance than 'A' grades, though.
Please avoid (!) using 'B' rated FSD modules. They do have the highest integrity of all FSD modules - about 10% more than 'A' - but there's a drawback: More weight. Only use 'B' if you depend on maximum reliability while you can abdicate on jump range performance.
'A' rated Frame Shift Drive modules are best in performance, but they're quite expensive. Their energy consumption is highest, too. Use these if jump range is the core of your space life.