the Gerber file

Gerber files are the package of files you hand to the factory to actually make your board — the industry-standard description of every copper layer, the solder mask, the silkscreen, and (with companion drill files) every hole. If the schematic is your idea and the layout is your drawing, the Gerbers are the precise instructions the fab machines read to turn that drawing into physical copper. They are the universal language between any EDA tool and any board house in the world.

Concretely, you export one Gerber file per layer: top copper, bottom copper, each inner layer, top and bottom solder mask, top and bottom silkscreen, and a board outline, plus a separate drill file (Excellon format) listing every hole's position and diameter. Each Gerber is essentially a set of instructions saying draw this shape here, flash this pad there, in precise coordinates. The fab loads them to make the photo-tools that etch the copper, the stencil for the mask, and the program that drives the drill. You typically zip the whole set together and upload it.

Why it matters: the Gerbers are the final handoff, the point of no return where your design leaves your screen and becomes a manufacturing order. A mistake here — a missing layer, the wrong drill file, mask and copper that do not line up — produces a wrong or scrap board, and you only find out when it arrives weeks later. So the discipline is to open your exported Gerbers in a separate Gerber viewer and inspect them as the fab will see them, layer by layer, before you ever upload. Many tools now also accept the newer all-in-one formats (like ODB++ or IPC-2581), but Gerber remains the lingua franca.