<hardware, standard> One of the series of standard sockets into which you can plug various x86 microprocessors. These vary in the number of pins, package, voltages, bus speeds, and supported processors. Motherboards often have clock multipliers so that the processor runs at a multiple of the bus speed.
Socket 2, 238 pin LIF/ZIF PGA (19x19), 5v, 25-50 MHz 486 SX, 486 DX, 486 DX2, 486 DX4, DX4 & Pentium Overdrive. Updated Socket 1, added support for Pentium Overdrive processors.
Socket 3, 237 pin LIF/ZIF PGA (19x19), 3.3/5v, 25-50 MHz 486 SX, 486 DX, 486 DX2, 486 DX4, DX4 & Pentium Overdrive. Supports 5V & 3.3V processors, considered the latest 486 socket.
Socket 4, 273 pin LIF/ZIF PGA (21x21), 5v, 60/66 MHz Pentium 60/66 and Pentium Overdrive, only 5v.
Socket 5, 296 pin LIF/ZIF, 320 pin LIF/ZIF SPGA (19x19 or 37x37), 3.3v, 50/60/66 MHz Pentium 75 - 133MHz, Pentium Overdrive, only 3.3v.
Socket 6, 235 pin ZIF PGA (19x19), 3.3v, 25-40MHz. Unpopular advanced Socket 3, rarely seen / paper spec 486 DX4, Pentium Overdrive, only 3.3v.