M/AM drives are used in warships and a few other quasi-governmental vessels. M/AM drives use anti-matter - anti-methane to be precise - and water to produce prodigous energy, but the fuel is intensely explosive, and a small ship could take out an entire city. M/AM ships are barred from atmospheric flight, and must be refueled in orbit. They are also available in various ratios of thrust to mass, but almost always are 1G or greater.
Jump drives are used to engage the wormhole network to travel between stars. The Jump drive must be used in certain places (Jump Gates) at exact vectors (Jump Vectors) to work, and instantaneously (to the crew and ship) move the ship through the wormhole to the exit point around the target star, retaining the Jump Vector, which is motionless relative to the target star.
Jump travel, while instantaneous to the crew, takes a varying amount of objective time - that is time relative to the systems connected by the wormhole net - depending on the number of successes the ship's Navigator has made for the transit. Jump Drives are rated in Factors, each Factor being 1*the current mass of the ship. A Factor of 2 would mean a ship could take another ship of the same mass through a jump safely, though Jump drives of Factors higher than 1 are extraordinarily uncommon on commercial ships other than Jump Tugs, which are used to ferry non-Jump capable spaceships between star systems.
Nomenclature note: Spaceships need only a Fusion or M/AM drive, as they only move in-system, whereas starships also need a Jump drive to move between systems.
Commercial ships are typically unarmed or lightly armed to fend off pirates or raiders. In wartime, commercial ships will sometimes be equipped with armament modules to better defend themselves, particularly if they are chartered by the Jeshen or an Allied Navy. Some smaller, more backward Human worlds will field a Navy of converted civilian ships. These are Fusion drive ships, and are slower, bulkier, and less heavily armed and armored than the equivalent purpose-built Navy ship. Others will buy refurbished retired ships from more advanced cultures which, while they may be a bit frayed around the edges and more or less antique, are at least constructed like proper fighting ships.