Timings, Latency. From the basic design nature of memory, it (the memory) cannot be accessed "right away" (think of a library: you may know exactly what the call-number for a book may be however you cant just walk in pooof have the book, gotta find or at least, get to the book). Everytime a [major] operative command is sent to memory there is a delay required before it can be completely processed and collectively these delays are known as timings or latencies and they are measured in clock cycles. While there are about a dozen or two timings related to memory, only a few are significant enough to mention (and they are dealt with in VFAQ Section). In general, the lower the timings, the better performance.