[Description] Ignitable, self-sustaining solid fuel/oxidiser mixture ("grain") with central hole and nozzle [Advantages] Simple, often no moving parts, reasonably good mass fraction, reasonable Isp. A thrust schedule can be designed into the grain. [Disadvantages] Throttling, burn termination, and reignition require special designs. Handling issues from ignitable mixture. Lower performance than liquid rockets. If grain cracks it can block nozzle with disastrous results. Grain cracks burn and widen during burn. Refueling harder than simply filling tanks. [Type] 
Solid rocket