What is a dimm referred to in a dimm slot?

A dimm slot on a computer motherboard is used to add extended memory or Ram ( random access memory ) all motherboards have a minimum and maximum amount of memory and memory speed which can be...

DIMM stands for Dual Inline Memory Module. This is the type of RAM that a computer uses.

DIMM stands for Dual In-line Memory Module. Have a look at the Wikipedia entry in the attached link. There is a picture on the rightihand side of the article of the DIMM slots on ta motherboard.

Having it in backwards, or having some kind of obstruction in the DIMM slot.

the different notch positions keep someone from installing a DDR DIMM or DDR2 DIMM in the wrong memory slot.