What does 8 GB RAM mean?

8GB refers to the RAM. This is memory on a chip that runs the hardware and the memory cache of the computer. The more RAM you have, the more you can do at once and the faster the computer is up to a point. iPhones combine RAM & storage. 8 GBs is enough for most tasks unless you edit videos for a living etc.

What is DIMM in RAM?

DIMM (dual in-line memory module) is a type of computer memory that is natively 64 bits, enabling fast data transfer. DIMM is a module that contains one or several random access memory (RAM) chips on a small circuit board with pins that connect it to the computer motherboard.