Intel is probably the most well known CPU manufacturer in the world. They've been making CPU's all the way from the earliest 8086 and are still designing and manufacturing CPU's to this day.
Even though in modern days, Intel CPU's only fit in Intel sockets and the other way around, in the old days there was a wide variety of manufacturers for any given CPU socket.
Socket 4 was released around 1993 and housed the very first real Pentium processor. Very few different CPU's have been made to fit this socket, which is limited to the Pentium 60MHz, the Pentium 66MHz and the obscure Pentium Overdrive which ran at either 120MHz or 133MHz. Because of the limited variety of CPU's manufactured for this socket and the limited speed options these motherboards provided, Socket 4 is a far less flexible platform when compared to Socket 3 or Socket 7. Socket 4 supported the then new 60MHz FSB and 66MHz FSB (even though some Socket 4 motherboards were made that had slower FSB's like 50MHz and 40MHz). Usually Socket 4 motherboards were fitted with ISA and PCI slots, though some VLB slotted Socket 4 motherboards were made. Socket 4 motherboards used either EDO or FPM memory modules and the memory modules had to be fitted in pairs where in it's predecessor, single modules were used. This was because Socket 4 was the first x86 motherboard that had a 64-bit memory bus (486 and earlier used a 32-bit memory bus).
All Socket 4 motherboards were made as AT motherboards or as proprietary boards. No ATX Socket 4 motherboards were ever made. No AGP slotted Socket 4 motherboard was ever made.