Normally when you eat pills, the drugs go straight into your body in one hit. You get an immediate high concentration of the drug, then nothing later. Timed Release drugs dissolve really slowly, so that they slowly go into your system over a much longer period, which means you don't have to keep taking them - you can take one, and it can last for quite a while - like 12 hours or something like that.

Maybe it's good to mention that this is usually written on pills that contain something similar to ephedrine - so if you are sensitive to ephedrine (or anything that is similar to amphetamines), maybe you should only take half or something to see if it's okay for you.