Everything about the packaging of memory chips rests on the concept of modules. These modules are vaguely like tiny motherboards within a motherboard, in that they, too, are integrated circuit boards. The big difference between DRAM and SDRAM is the synchronization feature. Be sure you understand how SDRAM uses timing cycles to more efficiently interrupt the CPU. Remember, SRAM is extremely fast and is used in secondary caches; SDRAM is a type of main memory.
It's all well and good to know how SDRAM differs from Rambus RAM, but you're also going to have to be able to differentiate between SIMMs and DIMMs. Inline memory modules are the small IC cards you install in your machine when you upgrade your memory. You won't have to remember clock speeds and the exact number of pins, but you'll definitely be tested on the different types of modules.