What is DIMM and SO-DIMM Slot?

Dual In line Memory Module ( DIMM ) :

The DIMM slots were introduced to cater for multitasking in computing devices. It began to replace Single In Line Memory Module ( SIMM ) as it supported high data flow and gave more options to the end user.

(DIMM slot)                                              (SO-DIMM slot)

As the requirement for RAM  keeps on increasing day by day, DIMM slot will give an option to the end user to increase the RAM space by using the 2nd DIMM port.DIMM port supports 64 bit data flow in contrast to 32 bit data flow in SIMM port. All Samsung notebooks are fitted with 2 DIMM ports for future enhancements.

In notebooks , Small outline Dual Input Memory Module (SO-DIMM) slots are used since there is lack of space in smaller and compact devices. SO-DIMM slots takes half the space in comparison to DIMM slots, but they draw higher power than its bigger variant. Please look at the representation above for reference.