DIMM is a very general term that applies to mostly all ram used since the first pentium processor. SDRAM is a subset of that but still a very general term (all DDR, DDR2 and DDR3 are all technically SDRAM) however SDRAM on its own usually refers to the memory standard which preceded DDR.
If both memories say DDR (and not DDR2/DDR3) then they should be the same type (assuming there both desktop memory).
However, as Upendra stated we will need more information than that. The following would be helpful:
- size and speed (model number) of the current ram
- mother board model
- specifically to find out what memory speed and size it supports, hopefully a QVL
- current ram configuration (how many slots used/free)
- desired upgrade (how much more ram do u wanna put in)