Short answers, pulled from the story.
A chisel is a hand tool with a wedge-shaped cutting edge used for carving or cutting hard materials such as wood, stone, or metal. The blade is forced into the material by pushing by hand, or by using a mallet or hammer. In industrial use, a hydraulic ram or falling weight may drive the chisel.
Woodworking chisels include the firmer chisel, bevel edge chisel, mortise chisel, paring chisel, skew chisel, dovetail chisel, butt chisel, carving chisel, corner chisel, flooring chisel, framing chisel, and drawer lock chisel. The slick is one of the largest types, used in timber frame construction and wooden shipbuilding.
A cold chisel is made of tempered steel and cuts cold metals without any heating torches or forges. A hot chisel cuts metal that has been heated in a forge until it softens, with the hotcut hardy being one type used in an anvil hardy hole.
The four common types of cold chisels are the flat chisel, the cross cut chisel, the round nose chisel, and the diamond point chisel. The flat chisel is the most widely known, the cross cut chisel cuts grooves and slots, the round nose chisel cuts oil ways in bearings, and the diamond point chisel cleans out corners.
A gouge is a specialized chisel whose blade is curved or angled in cross-section rather than flat. Its shape is described by a sweep number, usually ranging from #1 for flat up to #9 for a semi-circle, plus the blade width, written as something like a #7-20mm.
Stone chisels are used to carve or cut stone, bricks, and concrete slabs. A brick bolster cuts bricks with a wide flat blade, while sculptors use a bent spoon chisel with a bevel on both sides. To increase force, stone chisels are often hit with heavier club hammers.