Welcome! Feel free to ask any questions you have; include pictures of any mysteries if you can and someone here will have the answer.
As to your fresh water system; most RVs have both an onboard fresh water tank and a connection for a hose so you can connect directly to city water. The fill for your water tank may not be anywhere near your city water hook-up, which is usually on the driver's side, as is the electrical hook-up and the dump valve or valves for the waste system
Your big electric plug is a standard 30 amp plug; this is a normal size for campground electrical hook-ups. You can get a 30 amp to 15 amp adapter (try Walmart in the RV stuff or
Amazon) so you can hook up to an ordinary household outlet at home.