CNC and software glossary: what do all these terms actually mean?

Machine & motion

Gantry: the moving bridge carrying the spindle. Spindle/router: the motor spinning the bit.
Home / homing: driving to limit switches to establish the machine's fixed origin. Work zero / datum: YOUR origin on the stock. (See the coordinates entry.)
Soft limits: controller-enforced travel boundaries. E-stop: the big red instant stop.
Lost steps: stepper motor missed commanded motion, so everything after is shifted. Backlash: slack reversing direction. Runout: bit wobble from center. Tram: spindle perpendicularity to the bed.

Feed rate: how fast the bit travels (in/min or mm/min). Plunge rate: descent speed into material.
RPM: spindle speed. Chip load: material each flute bites per rev = feed ÷ (RPM × flutes); THE health number (see burning entry).
DOC / pass depth: depth of cut per pass. WOC / stepover: sideways bite per pass; on 3D finishing, the ridge-spacing quality knob.
Climb vs conventional: cut direction vs rotation (see that entry). Tearout / chipout / fuzzies: fibers torn instead of sheared.

End mill (flat), ballnose (round tip), V-bit (angled point), tapered ballnose (stiff cone + tiny ball), compression (up+down flutes), surfacing bit (wide flattener). See the bit-selection entry.
Flutes: cutting edges. Collet: the tapered sleeve gripping the shank. Shank: the held end.

Vector: the line/curve geometry toolpaths follow; open vs closed matters constantly (see open-vector entries). Node: a control point on a vector. Bitmap: a pixel image (needs tracing).
Toolpath: the computed cutting route. Post-processor: the translator to your controller's G-code dialect. G-code: the machine instructions.
Component: a 3D shape in the software's raster/heightmap format; the Component Tree combines them. Resolution: the heightmap density (set at Job Setup!). Bake: flatten dynamic properties into a fixed shape.
V-carve: variable-depth carving with an angled bit. Flat depth: the depth cap. Start depth: surface offset where cutting begins (see that entry!).
Tabs: holding bridges on cutouts. Onion skin: thin layer left instead. Spoilboard: the sacrificial bed. Machining allowance: material deliberately left for the next pass.
.crv / .crv3d: VCarve Pro saves .crv files and Aspire saves .crv3d files; a .crv3d file is only compatible with Aspire (see the compatibility entries). Gadget: a plug-in utility. Nesting: auto-arranging parts on a sheet.