Perfboard

Perfboard is a material for prototyping electronic circuits (also called DOT PCB). It is a thin, rigid sheet with holes pre-drilled at standard intervals across a grid, usually a square grid of 2.54 mm (0.1 in) spacing. These holes are ringed by round or square copper pads, though bare boards are also available. Inexpensive perfboard may have pads on only one side of the board, while better quality perfboard can have pads on both sides (plate-through holes). Since each pad is electrically isolated, the builder makes all connections with either wire wrap or miniature point to point wiring techniques. Discrete components are soldered to the prototype board such as resistors, capacitors, and integrated circuits. The substrate is typically made of paper laminated with phenolic resin (such as FR-2) or a fiberglass-reinforced epoxy laminate (FR-4).

The 0.1 in grid system accommodates integrated circuits in DIP packages and many other types of through-hole components. Perfboard is not designed for prototyping surface mount devices.

Before building a circuit on perfboard, the locations of the components and connections are typically planned in detail on paper or with software tools. Small scale prototypes, however, are often built ad hoc, using an oversized perfboard.

Software for PCB layout can often be used to generate perfboard layouts as well. In this case, the designer positions the components so all leads fall on intersections of a 0.1 in grid. When routing the connections more than 2 copper layers can be used, as multiple overlaps are not a problem for insulated wires.

...
Wikipedia