What kind of memory is commonly associated with the memory modules in today’s modern PCs?

The most commonly used types today are DIMMs (Dual In-Line Memory Module) and these are the small circuit boards that holds memory chips. 

Latest one is

DDR3-SDRAM - Double Data Rate Three (3) Synchronous Dynamic Random Access Memory

As a RAM DDR3

DDR3 RAMs 

SDRAM

DDR Memory Modules. Nowadays it's DDR3 and soon they will be slowly replaced by DDR4