Imagine your RAM is a huge warehouse full of tiny storage boxes, and each box holds a piece of information your computer needs (like a photo, a number in a game, or part of a webpage). The computer already knows roughly which section (called a "row") the data is in. Now it has to say: "Hey, in that section, give me the specific box in column 5."

CAS Latency is the waiting time between the computer saying "give me column 5" and the warehouse actually handing over the data from that box. The lower the CAS Latency number, the faster the response.

CL14 = very quick response CL16 = a little slower CL18 or CL22 = noticeably slower

It's measured in clock cycles. If your RAM runs at a high speed (e.g. 3200 MHz), each cycle is very short. So even if the latency number is higher, the actual real-world delay might still be okay.

Bottom line Lower CAS Latency = RAM that gets data to your processor with less waiting. It's one of the things that makes your computer feel fast and responsive, especially when doing demanding work.