One of the neat things about having an insulin pump is the fact that you can customize your pump to give you a basal rate of insulin to more closely match what your body would actually do. I am not referring to bolus insulin levels when you are eating, but basal levels to sustain a healthy blood sugar level. Your body does not act the same way all the time, if it did, a lot of things would be much easier, including the management of your diabetes. When you wake up in the morning, your body may require a certain amount of insulin to keep your blood sugars under control, however, as the day goes on and your activity levels change, your body has a different level of insulin required to sustain your blood sugars. Then in your evening hours, body requirements can change again, and one more time during the night when you are asleep.
Under traditional syringe based therapy, you will be giving yourself one or two "long-acting" insulin injections a day that are meant to give you a steady stream of insulin over the course of 24 hours. These rates cannot be changed or adjusted much (if at all) based on how that type of insulin works. However, with the insulin pump, you can set multiple rates to cover the 24 hours in a day. These rates will give you the fast-acting insulin that is in your insulin pump, but (virtually) continuously over the course of the day. Myself, I use four different rates during a 24 hour period.
The fine tuning of these rates are often done with regular visits to your diabetes nurse educator or endocrinologist. Ensuring you have your insulin rates correctly calibrated for your food intake (i.e. your bolus rates) is important for your overall blood sugar levels (ultimately your HA1C tests), however, in relation to your entire day, your basal rates affect you the whole day, not simply for periods of eating (as your bolus rates do). These rates are important to have done and done right. Not only can the proper calibration of these rates ensure your blood sugars do not stay high, they will also protect you from going into hypoglycemia. Basically what I am saying is, "Don't mess around them, unless you know what you are doing."