Sockets have to do with Processors. Each processor fits in a certain socket. Put the wrong processor in the wrong socket and it won't work and will damage you PC.
Pins have to do with RAM or PCI-E Components. RAM modules have a certain amount of pins that will fit in a certain DIMM. PCI-E also uses this term to find out if it will fit in your PCI-E.
LGA uses flat pads for the processor sockets instead of pins.
2 sockets
staggered pin grid array (SPGA)
Parallel sockets are wide, with two rows of pins that total 25 in all. Printers and some other devices use 36 pins, but they look the same. There is a screw hole at either end to allow the connector to be fastened securely.
LGA Sockets, most often used by Intel place the CPU Pins in the motherboard instead of on the CPU. For your viewing pleasure: PGA Sockets place the pins on the CPU BGA Sockets solder the CPU to the motherboard, and use rounded beads instead of obvious pins Slot Sockets look and behave in a manner similar to PCI, and have card slot arrays instead of individual pins DIP Sockets place the pins only on the outer edges of the chip. These are old and crude. PLCC Sockets have metal fins on all four sides, with a small chip that fits inside. This chip has receiving points that are flat against the chip, giving them an appearance similar to that of a game cartridge. (Some New BIOS chips still use this. Little chip nested inside of a brown plastic square) Think thats about it, though I'm sure there's a socket type I missed somewhere!
usually a 3 pin connector is used for a fan that can be controlled. The 3 pins are active ground and sense (the reporting of fan speed)
A socket is a receptacle (hole) into which you insert a pin. The number of holes determines the number of pins.
The PGA socket has pins on the bottom of the package aligned in uniform rows. The SPGA socket has pins on the bottom of the package that are staggered to squeeze more pins into a small space.
If you mean which kind is already in your computer, going to your start menu to Accessories and opening System Tools, then System Information gives you an overview of what kind of components your computer is utilizing. You can also go to your manufacturer's website and look up your model. As for telling the difference between the memory you're looking at outside of the computer, usually when you buy the RAM it will have DDR2 or 3 in the name of the component itself. DDR2 RAM has either 200 or 240 pins on it (the little gold metal "legs" sticking out of the component) though this is something of a bother to count. The number of pins is the same on both sides though, so if there are 100 or 120 pins on one side, it's DDR2.
a
SODIMM 200 PIN or 72 for 32bit processor
You don't want to bend the pins