Not all ships can launch drones: you need a drone bay internal module to do so. There are drone bays of different sizes that can host different numbers of active drones -ranging from 1 for the smallest bays to about 8+ for the larger bays. Corvettes and frigates will have trouble carrying lots of drones without sacrificing other capabilities.
Drones are managed in the following manner in Ceres: you may carry as many spare drones as you can on your ship, but only a small number can be active -the number allowed by the drone bay. This is due to the logistic needs of a drone: you need to have the right spares, the right ammunition and other things specific to each one of them -all of which have to be available in the bay.
There are eight types of drones, and several models for each type of drones:
Spy drones are unarmed but are equipped with medium-range passive sensors: they act as scouts or sentries in dangerous areas where you are not willing to risk a whole ship.
They are half-the-size of the standard drone, so they can be carried in greater numbers in drone bays. This comes at a cost though: they are the only drones that are expandable. Once released, they have a limited run.
The utility drones are encountered everytwhere as they are used for all kinds of tasks. They mine asteroids, gather debris, resource and cargo but also repair other ships or installations. You should never leave home without them, or use them in environments where you can loose them.
The gauss gun drones are the cheapest of all offensive drones. They carry a foldable electro-magnetic gun that fires small shells at their targets. Their gun is smaller than the ones used on ships, and their targeting suite rather more primitive too.
Do not expect them to attack anything larger than a corvette and survive, but when used in swarms they may prove bothersome.
The laser drones are the second cheapest of the drones equipped for attack. They house a small laser and are nimble enough to be a bit more than a nuisance to their target. They are great at taking out small or unarmored units, and when used in great numbers, they may distract an enemy enough so as to help you escape or carry your attack with greater success.
Missile drones are little mobile missile launchers -with just enough thruster power to get into range, maneuver, attack and come back to re-arm. They are directly supplied with missiles from the mothership ammunition stores: when they carry advanced weapons, they can pack quite a punch. Then again, if your ship has good point-defense, neither missile nor drone is likely to make any lasting impression.
Plasma drones are basically self-propelled plasma chambers -they are the larger weapon mounted on the smallest hull. At close range they can be devastating. If they can get to close range, that is.
Defense drones are basically a mobile point-defense mount. They orbit around your ship or a specified location and provide protection from missiles, torpedoes, fighters and other drones. They are expensive and hard to find, although they are rumors that the Hydra faction is making very advanced models in great numbers.
Boarding drones are advanced robotic penetrators, mobile nano-factories in their own right. Their mission is to latch onto enemy ships to damage and hack systems. They do so by directly hacking through the external sensor array of the target ship and by releasing creepers: little micro-robots that will seek hull breaches and other weak spots and enter the ship itself.
Such advanced capabilities do not come cheap: boarding drones are delicate and expensive machines that only technologically advanced factions manufacture.
Drones can be launched in two different ways. Either by the quick-order menu when clicking on a ship or object, either by the drone sub-menu at the bottom right of the screen. When launching drones with this last method, the drone will automatically select a target.
Utility drones can also be activated by the the gather button (that doubles up as mineral counter).