When it comes to the physical RAM we have two form factors to consider: DIMM and SO-DIMM. This is the "packaging" of the RAM chips (DRAM, SRAM, and SDRAM) and is how we plug the physical RAM into a system for utilisation by the operating system.
DIMM stands for "Dual In-Line Memory Module". It's the physical form factor of the RAM that you put inside of a desktop computer or a server. It's the larger of the two form factors and can be seen in the picture below.
SO-DIMM is a more compact form factor of DRAM and is extremely common in laptops and other small form factor machines. Here's a picture of some SO-DIMM:
You're not likely to ever really see the physical packaging of RAM unless you build a computer and or a laptop (which is even rarer.)