A RAM module has gone out on your laptop and requires replacement. Without opening the laptop up or possessing any additional knowledge about your system, you know that you will most likely need to replace the module with a ______ type module.
Laptop and mobile devices typically utilize SO-DIMM type RAM modules, as these modules are smaller in form factor than typical DIMM modules.
While DDR 3 or DDR 4 could be an answer, this would require more detailed information about the motherboard on your system.
If you got this one right, you're not SO DIMM.
(Sorry for the pun; I couldn't help myself)