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You have a "black" tank which your toilet sits directly on, and there is a Thetford valve on the outside underneath of your trailer to allow the sewage to be drained out. Look in the rear bumper compartment, there may be a "slinky" there to allow connection for draining.
Your sinks and shower are connected directly to the same waste valve; there is no holding tank for them. You need to be connected to a sewage system in an RV park in order to use them, or parked in an area that allows the draining of so-called "gray" water right onto the ground. Such places are very rare these days.
Hope this helps you understand, but if not, just fire away again with the questions!