RAM timings are very simple to understand. Those are the delays your processor must wait for information. Processors are alot faster then modern RAM. The lower the timings, the faster information shall arrive.
Good OC RAM are G Skill LA's or OCZ Platinum Rev2. These all have low latency of course. When your OC demands get high, you will need to loosen your RAM timings. Because data cannot move at very high speeds with low latency.