Nini, we might as well learn together here... I'm a beginner too.
Let's start with pH. pH stands for the power of Hydrogen, which basically means it is a measurement of the acidity and alkalinity levels. I'm going to quote from
About.com here. Therefore, your pH level is right in the middle. I've been told that between 8.0-8.4 was good but someone may correct me here.
Decaying matter, waste from creatures in your tank, excess food, as well as water pumped through fish gills will add to ammonia in your tank. Everyone recommends that ammonia levels be zero in the tank because ammonia becomes toxic (poisonous) very quickly, especially in a saltwater environment. So CONGRATS!
You have the right amount of ammonia in your tank - zero!
Since your ammonia, nitrite and nitrate levels are zero or near zero, you've gone through nitrogen cycling in your tank already, I presume. The nitrogen cycling process is the way to make your tank into a little ecosystem. Good job! You're doing much better than I did, when I got my octopus.
During the cycling of your tank, the ammonia will get transformed into nitrite by bacteria, which can be again toxic to creatures in your tank. But again, great! Your levels are zero.
Nitrite was needed to start off the 3rd part of the cycle. Nitrobacters are bacteria that feed on Nitrite and their waste produces Nitrate. You need nitrobacters in your tank to help get rid of the "bio-load" which are the things that create ammonia. See the cycle?
You basically want to grow this bacteria so the waste in your tank won't decompose and become ammonia. But to grow this bacteria, you needed to make your tank poisonous for a little while. So your levels are saying, you've finished the first poisonous stage (ammonia = 0), and the 2nd poisonous stage (nitrite = 0), and you are well into your third stage (nitrate = 0-5ppm).
That's about all I know. I'll do a little more research over the next few days about your other parameters and see if I can come up with some more help for you.
Hopefully, somebody with a lot more experience than I do (I've only been doing this for less than 6 months) can help you out with the rest of the information.