Depending on how your dishwasher was originally installed, you might have access to the water supply and drain lines leading to and from the dishwasher. Inspecting the connections that you have access to, typically near the main kitchen sink, you can determine if there are any leaks. You can tighten any connections you have to eliminate leaks, but you may also have deteriorating lines. Depending on the age and performance of your dishwasher, you occasionally may have to replace the unit and the water and drainage lines.
Most dishwashers today are installed under a countertop and next to a sink. The dishwasher usually connects to a water line under the sink, and also has a drain line that hooks up to the drain under the sink. If these connections go bad, replacing them is a difficult task that usually requires a professional plumber to fix for you.
A dangerous aspect of a dishwasher includes the electrical connections to the unit. It is also difficult to get out from under the counter. But if you are interested in learning how it all works, here is great video from RepairClinic.com